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Journal  of 


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A  TEXT-BOOK 


OF: 


CHEMISTRY  if  D  CHEMICAL 
URANALTSIS  EOR  NURSES 


BY 


HAKOLD  L.  AMOSS,  S.B.,  S.M.,  M.D.,  DE.  P.  H. 

FORMERLY  CHEMIST,  HYGIENIC    LABORATORY,  UNITED    STATES  PUBLIC    HEALTH  SERVICE  ; 

PHYSIOLOGICAL  CHEMIST,  UNITED  STATES  BUREAU  OF  CHEMISTRY;  INSTRUCTOR 

IN  PHYSIOLOGICAL   CHEMISTRY,    GEORGE  WASHINGTON    UNIVERSITY 

MEDICAL  SCHOOL,  WASHINGTON,  D.    C.  J  ASSISTANT  IN 

PREVENTIVE  MEDICINE,  HARVARD  MEDICAL 

SCHOOL,  BOSTON,  MASS.,   ETC. 


LEA    &   FEBIGER 

PHILADELPHIA  AND  NEW  YORK 
1915 


LIBRARY 
D    ' 


GIFT  PAG  MO    >,  -RNAL 

OF   NURoING  TO  H/Jii-.Jc   DEPT.j 

Entered  according  to  the  Act  of  Congress,  in  the  year  1915,  by 

LEA  &  FEBIGER, 
in  the  Office  of  the  Librarian  of  Congress.     All  rights  reserved. 


Jt      a'  /?' 


PKEFACE. 


THE  demand  for  a  simple  book  on  chemistry,  written 
especially  for,  and  adapted  to,  the  needs  of  the  nurse, 
has  become  more  and  more  urgent  with  the  institution 
of  regular  courses  on  chemistry  in  the  best  training 
schools.  In  the  preparation  of  this  work  the  author 
has  endeavored  to  cover  the  subject  briefly  and  clearly, 
and  in  an  interesting  style,  so  that  the  reader  may 
easily  absorb  and  assimilate  the  material  presented. 

It  is  not  to  be  questioned  that  the  more  chemistry  a 
nurse  knows  in  usable  form  the  greater  her  value  to  the 
patient  and  to  the  physician.  In  many  cases  the 
important  measure  of  feeding  the  sick  is  left  to  the 
nurse.  In  most  instances  her  empirical  knowledge  of 
dietetics  may  guide  her  aright.  Yet  it  is  obvious  that 
some  knowledge  of  the  chemical  composition  of  food- 
stuffs and  of  the  chemical  processes  of  digestion  and 
assimilation  will  better  serve  her  in  cases  of  unusual 
type  and  those  presenting  metabolic  and  digestive 
disturbance.  If  the  nurse  knows  no  chemistry,  how 
can  she  be  expected  always  to  remember  that  starches 
yield  sugars  and  are  to  be  given  to  the  diabetic  with 
extreme  caution?  What  can  the  term  Calorie  mean 
to  her?  There  are  other  questions,  too,  of  drug  admin- 

743509 


IV  PREFACE 

istration  and  application,  of  the  collection  and  preser- 
vation of  specimens,  and  of  discerning  observation. 

It  is  the  author's  impression  that  chemistry  has 
not  yet  received  the  attention  in  undergraduate  and 
graduate  instruction  of  nurses  that  its  importance 
merits.  He  believes  that  one  of  the  chief  reasons  is 
that  few  teachers  have  the  time  to  collect  and  put 
into  simple  form  the  material  necessary  for  the  nurse's 
foundation  and  understanding  in  chemistry. 

In  this  volume  the  author  has  striven  for  simplicity 
and  a  gradual  logical  development  of  the  subject;  and 
he  hopes  that  the  book  will  adequately  fill  the  place 
in  nursing  education  for  which  it  was  designed. 

H.  L.  A. 

NEW  YORK,  1915. 


CONTENTS. 


CHAPTER  I. 
THE  SLAKING  OF  LIME       ....  .....       19 

CHAPTER  II. 
WEIGHTS  AND  MEASURES 24 

CHAPTER   III. 
THE  METALS      ...... '  .       25 

CHAPTER  IV. 

MOLECULES  AND  ATOMS     .     -,     .      .     .      .....       30 

CHAPTER  V. 
CHEMICAL  PROCESSES 34 

CHAPTER  VI. 
ATOMIC  WEIGHTS .       39 

CHAPTER  VII. 
OXYGEN    .      .      .      .      .      ..._..      .      .      .      .      .       43 

CHAPTER    VIII. 

HYDROGEN  .      .  ' 48 


CHAPTER  IX. 
WATER  


vi  CONTENTS 

CHAPTER  X. 
HEAT        ...     .     V*  . 60 

CHAPTER  XI. 

SOLUTIONS  AND  PURIFICATION  OF  SUBSTANCES       ...       64 

CHAPTER  XII. 
NATURAL  WATERS — CHEMICAL  ACTION  OF  WATER      .      .       68 

CHAPTER  XIII. 
COMPOSITION  OF  WATER 72 

CHAPTER  XIV. 

HYDROGEN  PEROXIDE    .     .     .     .     .     ...    .     .     .     .     .       77 

CHAPTER  XV. 
CHLORINE ^.  81 

CHAPTER  XVI. 

BROMINE — IODINE — FLUORINE 89 

CHAPTER  XVII. 
SULPHUR ;     .     .     .     .....      .       95 

CHAPTER  XVIII. 
SODIUM     ......     ......     .     .     .     .     .     .     100 

CHAPTER  XIX. 
ACIDS  AND  BASES — POTASSIUM     .      .     .      .     .     .     .     .     106 

CHAPTER  XX. 
PHOSPHORUS — ARSENIC — ANTIMONY — BISMUTH  112 


CONTENTS  vii 

CHAPTER  XXI. 

CALCIUM  .     . .     .     .     .      .      .      .     119 

CHAPTER  XXII. 
MAGNESIUM  GROUP       .      .      .      .      .     .      .     .     .      .      .     123 

CHAPTER  XXIII. 
ALUMINUM — IRON — MANGANESE   .      .     .....      .     129 

CHAPTER  XXIV. 
LEAD — SILVER — PLATINUM       .      .     . 133 

CHAPTER  XXV. 
CARBON    .     .     .     .     . 138 

CHAPTER  XXVI. 
COMPOUNDS  OF  CARBON  WITH  HYDROGEN  .     .     .     .     .     141 

CHAPTER  XXVII. 
ETHERS .     .     .".'.-     .     .      .      .     150 

CHAPTER  XXVIII. 
THE  MARSH  GAS  SERIES  .      .........      .     153 

CHAPTER  XXIX. 

THE  PARAFFINS       ...     .     .     ...     ..    .     .     -     160 

CHAPTER  XXX. 
SUGARS     ....     ."     ;     .     .     .     .      .      .      .      .      .     165 

CHAPTER  XXXI. 

POLYSACCHARIDS  173 


Vlll  CONTENTS 

CHAPTER  XXXII. 
THE  DIGESTION  OF  CARBOHYDRATES 180 

CHAPTER  XXXIII. 
FATS 183 

CHAPTER  XXXIV. 
BENZENE  SERIES 191 

CHAPTER  XXXV. 
NITROGEN      .      .      .      .     . 202 

CHAPTER  XXXVI. 

OTHER  NITROGEN  COMPOUNDS .     .     208 

CHAPTER  XXXVII. 
PROTEINS .     .     ...      .  .      .     216 

CHAPTER  XXXVIII. 
THE  BLOOD 226 

CHAPTER  XXXIX. 
MILK  .      ...     . .     .     235 

CHAPTER  XL. 
THE  URINE    .     .     .    • 240 

CHAPTER  XLI. 
URANALYSIS  .  249 


TO  THE  INSTRUCTOR. 


MANY  students  of  medicine  and  nurses  find  the 
particular  chemistry  which  they  need  very  difficult  to 
acquire.  Obviously,  the  manner  of  presentation  of  the 
subject  will  affect  largely  the  results,  especially  in  the 
training  school  where  the  all-important  demonstration 
facilities  are  usually  lacking  and  where  there  is  rela- 
tively little  time  devoted  to  the  teaching  of  chemistry. 
It  is  exceedingly  difficult  to  really  grasp  this  subject 
by  reading  or  listening  to  lectures  unaccompanied  by 
experimental  work,  and  the  student  is  soon  found 
simply  attempting  to  memorize  a  large  number  of 
isolated  facts.  Especially  is  this  true  in  the  beginning, 
and  chemistry  soon  becomes  a  hopeless  muddle. 
Demonstrations,  therefore,  are  urgently  recommended, 
and  whenever  possible  even  a  small  number  of  labora- 
tory exercises  should  be  arranged  so  that  the  student 
can  handle  the  test-tube  and  chemicals.  In  this  man- 
ner it  is  often  possible  to  make  the  subject  fascinating 
and  interesting  instead  of  drudgery.  This  compila- 
tion is  necessarily  limited  to  those  subjects  which  the 
efficient  nurse  must  know:  many  processes  of  which 
all  educated  persons  should  possess  at  least  a  little 
knowledge  have  been  omitted.  If  the  student  acquires 
2 


18  TO  THE  INSTRUCTOR 

fundamental  ideas  of  chemistry  these  things  will  come 
easily  later  in  their  general  reading. 

However,  it  is  not  to  be  expected  that  the  average 
student  will  digest  all  the  matter  contained  herein. 
Enough  has  been  left  in  the  reduction  of  the  original 
manuscript  to  satisfy  the  interested  student  and  not 
too  much  to  frighten  the  uninterested. 

An  attempt  is  made  to  develop  the  subject  from  the 
simplest  and  more  familiar  phenomena.  Since  the 
interest  of  the  author  was  first  aroused  in  this  subject 
by  the  slaking  of  lime  this  is  made  the  foundation 
for  the  introduction  of  the  nurse  to  this  important 
science. 


CHEMISTRY  FOR  f  URSES. 


CHAPTER  I. 
THE  SLAKING  OF  LIME. 

WHEN  water  is  poured  over  quicklime,  heat  is  gen- 
erated and  the  water  soon  begins  to  boil.  If  water  is 
poured  on  the  same  amount  of  limestone  from  which 
the  lime  is  made  we  obtain  no  change  in  temperature 
and  no  heat  is  generated;  hence,  there  must  be  some 
change  other  than  the  physical  contact  of  the  lime 
and  water  in  order  to  produce  this  large  amount  of 
heat.  If  there  is  such  a  change,  what  does  it  amount 
to  and  how  is  it  produced?  Quicklime  is  made  by  heat- 
ing very  intensely  and  over  a  rather  long  period  of 
time  the  stones  we  know  as  limestone  rock.  If  we 
heat  absolutely  dry  limestone  in  the  kiln  for  some 
hours  we  find  by  reweighing  it  from  time  to  time 
that  it  gradually  loses  weight.  Continuing  the  heating 
processes  we  find  that  we  arrive  at  a  stage  where 
it  no  longer  loses  weight,  that  is,  we  have  heated 
it  to  constant  weight,  and  no  amount  of  heating  can 
reduce  the  weight  further.  Curiously  enough,  the 
loss  is  always  44  pounds  in  a  hundred.  What  does  it 
mean  then  if  we  take  several  samples  of  pure  dry 


20  THE  SLAKING  OF  LIME 

limestone  and  heat  it  in  the  kiln  to  constant  weight 
ahd  find  that  exactly  44  out  of  every  100  pounds  is 
lost-?  -.Can  we  not  say,  first,  that  the  limestone  probably 
has  '  a:  definite  ;cqmposition — that  is,  it  is  composed 
of  certain  definite  materials,  and  second  that  these 
materials  whatever  they  are  occur  in  the  same  propor- 
tion each  time? 

During  this  process  of  heating,  when  the  limestone 
is  being  transformed  into  lime,  the  physical  characters 
of  the  limestone  undergo  marked  changes,  chief  among 
them  is  the  change  from  a  hard,  granular  substance  to 
a  smooth,  friable,  soft  material.  But  what  happens 
during  the  heating?  It  will  be  shown  later,  that  this 
44  pounds  out  of  a  hundred  which  is  given  off  is  the 
same  gas  that  we  give  off  constantly  from  our  lungs, 
namely,  carbon  dioxide.  And  the  driving  off  of  this 
gas  by  heat  is  a  chemical  process  and  a  chemical 
change  is  brought  about.  We  could  grind  the  original 
limestone  into  a  very  fine  powder — that  would  be  a 
physical  change — yet  on  pouring  water  over  it  we  would 
get  no  heat.  If  on  the  other  hand  we  raise  this  powder 
to  red  heat  for  several  hours,  we  have  driven  off  a 
part  of  it  though  we  can  not  see  it  come  off  and  have 
produced  a  change  in  the  internal  structure  of  the 
substance  (chemical  change).  We  also  witness  a 
chemical  change  when  water  is  added  to  the  lime. 
Suppose  that  we  add  to  our  56  pounds  of  lime  result- 
ing from  the  heating  of  100  pounds  of  limestone,  a 
hundred  pounds  of  water  at  room  temperature 
(68°  F.)  and  stir  for  a  few  minutes — always  the 
temperature  of  the  water  increases  the  same  number 


THE  SLAKING  OF  LIME  21 

of  degrees  it  makes  no  difference  how  many  experi- 
ments you  make.  Then  again  there  must  be  some 
definite  and  always  constant  change  taking  place 
when  water  is  poured  on  lime.  Now  if  we  try  to 
recover  our  hundred  pounds  of  water  by  distillation 
(a  physical  process)  we  find  that  at  the  temperature 
of  boiling  water  (212°  F.),  we  can  recover  only  82 
pounds  of  the  100  pounds  of  water  which  we  added. 
Therefore  18  pounds  of  water  must  have  been  fixed 
to  the  quicklime  in  the  slaking  process.  There  must 
have  been  some  chemical  change  also  for  our  lime  is 
no  longer  a  smooth  non-crystallizing  substance  but 
consists  of  clear  crystals  having  definite  angles.  Since 
water  or  some  of  the  constituents  of  water  has  been 
added  to  our  quicklime  we  can  call  this  new  crystallized 
substance  hydrated  lime.  This  new  product  weighs 
74  pounds  and  does  not  give  off  water  when  heated  to 
boiling  point.  If  now  we  heat  our  dry  hydrated 
lime  to  a  higher  degree  it  begins  to  lose  weight  and 
water  is  given  off  until  finally  the  whole  of  the  18  pounds 
of  water  is  recovered  and  we  have  56  pounds  of  quick- 
lime left,  having  properties  identical  with  those  before 
described.  This  is  another  chemical  change — the  water 
was  driven  off  by  the  heat  leaving  behind  a  compound 
with  different  physical  properties. 

Suppose  we  add  again  to  our  56  pounds  of  quicklime 
100  pounds  of  water.  When  the  solution  has  cooled 
and  settled  clear,  remove  a  small  portion  in  a  test-tube 
and  blow  through  it  by  means  of  a  glass  tube.  The 
clear  solution  becomes  turbid  and  a  white  precipitate 
is  formed.  Suppose  we  bubble  by  means  of  a  blower 


THE  SLAKING  OF  LIME 

the  used  air  which  collects  in  the  top  of  a  theatre  or 
the  gases  given  off  from  a  lime  kiln,  through  our  mix- 
ture of  56  pounds  of  quicklime  and  100  pounds  of 
water.  Finally  there  comes  a  stage  when  our  breath 
bubbled  through  the  clear  solution  no  longer  causes 
turbidity.  Now  should  we  distill  the  water  and  weigh 
it,  provided  none  has  been  accidentally  lost  in  the 
operation  we  find  that  it  weighs  100  pounds.  Obviously 
something  has  replaced  the  18  pounds  of  water  which 
in  the  first  instance  was  held  in  chemical  combination 
by  the  quicklime.  Furthermore,  our  white  residue 
now  weighs  100  pounds  and  chemical  tests  show  us 
that  this  substance  is  identical  with  the  limestone 
which  we  started  with.  We  know  that  the  carbon 
dioxide  in  the  expired  breath  has  combined  with  the 
hydrated  lime  to  form  limestone.  Then  we  can  now 
call  limestone  carbonated  lime.  These  are  examples  of 
chemical  changes.  We  have  learned  that  no  chemical 
change  takes  place  without  a  corresponding  physical 
change  and  also  that  these  chemical  compounds  unite 
in  definite  proportions.  Having  once  learned  by 
experiment  how  much  of  one  substance  is  held  in 
chemical  union  with  another  we  are  able  to  predict 
before  we  put  these  substances  together  just  what 
will  happen  and  to  calculate  how  much  substance  we 
shall  have  at  the  end  of  our  experiment. 

SUMMARY  OF  CHAPTER  I. 

A  physical  change  means  a  change  in  form,  as  the 
grinding  of  limestone.  The  freezing  of  water,  and  its 
conversion  into  steam  are  examples  of  physical  changes. 


SUMMARY  OF  CHAPTER  I  23 

In  a  physical  change  the  form  or  state  of  a  substance 
is  changed  while  the  intrinsic  chemical  properties  are 
not  altered. 

A  chemical  change  means  a  change  in  composition. 
It  was  shown  that  the  heating  of  limestone  causes  a 
chemical  change:  a  gas  (carbon  dioxide)  is  given  off 
and  the  substance  left  is  lime  which  has  physical  and 
chemical  properties  totally  different  from  limestone. 
When  water  is  added  to  lime  a  chemical  change  takes 
place;  a  new  compound  possessing  new  properties  is 
formed.  Heat  is  given  off.  In  all  chemical  changes 
heat  is  either  absorbed  or  given  off. 

In  any  chemical  change  there  is  always  a  physical 
change;  the  reverse  is  never  true. 

Pure  chemical  substances  contain  definite  elements 
in  definite  proportions. 


CHAPTER  IT. 
WEIGHTS  AND  MEASURES. 

IN  our  experiments  with  quicklime  and  water  we 
used  such  quantities  stated  in  such  terms  as  we  can 
readily  appreciate.  As  a  matter  of  fact  in  order  to 
obtain  absolutely  accurate  results  we  must  use  very 
small  quantities.  We  used  100  pounds  so  that  we 
should  not  be  confused  by  decimals.  In  chemical 
work  the  metric  system  is  used  in  all  countries.  One 
kilogram  (abbreviation  kilo  or  k)  is  equivalent  to  2.2 
pounds.  One  thousandth  of  a  kilogram,  a  gram,  is 
used  as  the  basis  of  the  metric  system;  about  454 
grams  equal  1  pound.  An  ounce  avoirdupois  equals 
about  28.5  grams.  Fifteen  to  twenty  drops  of  pure 
water  weigh  1  gram,  and  the  volume  occupied  by  this 
amount  of  water  is  equal  to  1  cubic  centimeter  (1  c.c.). 
Decigram,  one  tenth  of  a  gram,  is  rarely  used,  but 
milligram  0.001  gm.  is  convenient  for  stating  the  doses 
of  the  more  active  medicinal  agents.  Sixty-five  milli- 
grams (0.065  gm.)  are  equivalent  to  1  grain.  . 


CHAPTER  III. 
THE  METALS. 

A  CLASS  of  substances  represented  by  gold,  silver, 
copper,  tin,  lead,  iron,  nickel,  quicksilver,  etc.,  pos- 
sessing the  power  of  conducting  heat  and  electricity, 
capable  of  being  fused,  moulded  and  of  being  drawn 
out  into  various  shapes,  and  having  a  peculiar  luster, 
are  known  to  us  as  metals.  Some  of  them  (gold,  silver, 
lead,  copper,  quicksilver,  etc.),  occur  in  comparatively 
large  quantities  as  metals  in  nature  and  they  also 
occur  in  combinations  with  other  substances  as  ores. 
With  one  exception  (quicksilver)  at  ordinary  tempera- 
tures they  are  solid. 

Rusting  of  the  Metals. — Our  most  common  example 
of  a  metal  is  iron.  This  metal  is  found  free  in  nature 
in  very  small  quantities.  Pure  iron  has  a  grayish- 
white  color  which  on  exposure  to  damp  air  soon  changes 
to  black  and  then  to  red.  In  the  process  of  color 
change,  physical  properties  of  the  metal  change:  if 
this  entire  piece  is  rusted  throughout  it  loses  its 
strength  and  crumbles,  it  can  no  longer  conduct 
electricity  or  be  hammered  into  various  shapes.  Its 
weight  increases.  The  rusting  process  can  be  hastened 
by  heating  in  the  air. 

The  Air  and  the  Rusting  Process. — A  piece  of  iron 
placed  in  a  glass  tube,  the  air  exhausted  and  the  tube 


26  THE  METALS 

sealed,  will  retain  forever  its  luster.  Even  heat  will 
not  bring  about  the  tarnishing  or  rusting  process  unless 
air  is  admitted.  Therefore  air  or  some  constituent  of 
air  is  necessary  for  rusting. 

Silver  will  rust  quickly,  turning  black,  when  heated 
in  air.  Let  us,  therefore,  place  some  silver  filings  in 
a  hard  glass  tube  and  heat  it  to  redness  and  allow  air 
to  pass  through  slowly  and  then  to  a  similar  tube 
containing  pieces  of  untarnished  iron.  So  long  as  the 
silver  continues  to  rust  the  iron  will  remain  untar- 
nished. Conduct  the  air,  which  has  passed  over  the 
heated  silver  and  iron  to  a  bell  jar  and  when  it  is 
collected  in  sufficient  quantities  place  in  it  a  mouse. 
The  mouse  dies  very  quickly.  Now  strike  a  match 
and  thrust  it  into  the  bell  jar — the  flame  goes  out. 
What  have  we  learned?  First,  that  the  substance  in 
the  air  which  causes  iron  to  rust  is  the  same  as  that 
which  brings  about  the  tarnishing  (rusting)  of  silver; 
second,  that  this  same  substance  is  also  necessary  for 
life;  third,  that  it  is  also  necessary  for  burning.  There- 
fore, we  reason  that  the  rusting  of  metals,  the  main- 
tenance of  life  by  respiration  and  the  burning  of  wood 
are  closely  related  if  not  the  same  processes. 

Oxygen. — To  continue  our  experiment,  let  us 
heat  some  of  the  rusted  silver  and  collect  the  gas 
given  off  in  the  process  by  conducting  it  into  a  bell 
jar.  Now  repeat  the  mouse  and  the  match  experiments 
with  this  new  gas  and  we  get  very  different  results. 
The  mouse  is  enlivened  and  the  match  burns  more 
brightly  than  in  ordinary  air.  These  results  lead  us 
to  believe  that  we  have  gotten  that  substance  in  the 


ELEMENTS  27 

air  essential  for  life  in  a  pure  state.  Other  experi- 
ments show  us  that  this  is  true.  Priestly,  an  English 
chemist,  who  afterward  came  to  America  and  settled 
at  Northumberland,  Pa.,  discovered  these  facts  by 
working  with  rusted  quicksilver  and  called  the  gas 
thus  obtained  dephlogisticated  air.  Lavoisier  later 
called  it  oxygen,  which  means  acid  producing,  thinking 
(erroneously)  that  this  substance  always  produces 
acid. 

Now  we  term  the  rusting  of  the  metals,  the  burning 
of  substances  and  the  various  vital  processes  in  the 
animal  body  where  oxygen  is  combined  with  other 
substances,  oxidations.  The  new  chemical  compounds 
thus  produced  are  known  as  the  oxides.  Iron  rust  is 
chemically  known  as  iron  oxide,  etc. 

Elements. — From  the  foregoing  we  have  learned 
that  there  are  at  least  two  gases  in  the  air  which  may 
be  easily  taken  out,  namely,  oxygen  and  carbon  dioxide. 
We  know  that  these  substances  exist  there  free  or  in 
other  words  air  is  a  mixture  of  gases.  As  has  been 
stated,  the  oxides  and  other  chemical  compounds  of 
metals  occur  in  the  earth  as  ores.  Here  we  have 
examples  of  both  compounds  and  mixtures;  the  oxide 
of  iron  is  a  compound  consisting  of  iron  and  oxygen  in 
chemical  union,  whereas  it  may  be  mixed  with  clay  or 
other  oxides  that  may  be  removed  mechanically. 
Then  a  mixture  may  be  analyzed  mechanically  but 
compounds  can  be  separated  into  their  constituents 
by  chemical  processes  only. 

In  the  process  of  chemical  analysis  we  arrive  at  a 
stage  where  we  can  no  longer  separate  the  various 


28  THE  METALS 

substances  into  simpler  materials.  Such  a  substance, 
which  can  no  longer  be  resolved  into  unlike  compo- 
nents, we  term  an  element.  The  metals  already  men- 
tioned are  elements.  Brass  is  an  alloy  or  mixture  of 
two  elements,  copper  and  zinc.  Oxygen  is  also  an 
element. 

Symbols. — For  simplicity,  convenience  and  economy 
in  writing  chemical  formula,  the  names  of  the  various 
elements  are  abbreviated  or  the  first  letter  alone  or 
combined  with  some  other  distinctive  letter  is  used; 
for  example,  O  means  oxygen  and  Os  osmium;  H 
means  hydrogen  and  He  helium;  S  sulphur  and  Si 
silicon.  We  hardly  see  how  Fe  stands  for  iron  or  Cu 
for  copper  until  we  remember  the  Latin  names  ferrum 
and  cuprum.  Then  if  an  oxide  of  iron  is  composed  of 
1  atom  of  iron  and  1  atom  of  oxygen  we  would  write 
it  thus  FeO;  if  in  another  oxide  of  iron  there  are  two 
atoms  of  iron  and  three  atoms  of  oxygen  we  write  it 
Fe2O3. 

SUMMARY  OF  CHAPTER  III. 

All  substances  can  be  analyzed  into  their  simple 
components  which  are  known  as  elements.  Metals 
(iron,  gold,  silver,  copper  and  mercury)  are  elements. 
They  cannot  be  further  separated  into  different  sub- 
stances. Oxygen  is  also  an  element.  It  is  a  gas  occur- 
ring in  the  air  and  is  necessary  to  life.  The  rusting  of 
metals  is  a  chemical  union  of  the  element  oxygen  with 
the  metals  (also  elements).  The  burning  of  wood  is 
also  ah  oxidation.  Therefore  oxidation  may  take 
place  quickly  resulting  in  the  production  of  heat  and 


SUMMARY  OF  CHAPTER  III  29 

a  flame  or  it  may  proceed  quietly  and  slowly  and  in 
the  presence  of  water.  In  either  case  oxidation  is  the 
same  and  the  total  amount  of  heat  given  off  is  exactly 
the  same. 

In  writing  chemical  reactions  symbols  are  made 
use  of  to  indicate  the  various  elements.  Usually  the 
first  letter,  capitalized,  is  used  as  the  symbol  for  the 
element,  O  =  oxygen,  H  =  hydrogen.  Sometimes  the 
first  two  letters,  as  Si  =  silicon  (S  =  sulphur).  Cu  = 
copper  (Latin,  cuprum) .  Ag  =  silver  (Latin,  argentum) . 


CHAPTER  IV. 
MOLECULES  AND  ATOMS. 

THE  smallest  particle  of  a  compound  which  can 
exist  is  called  a  molecule.  The  size  of  molecules  vary 
but  they  are  inconceivably  small.  Since  compounds 
are  made  up  of  two  or  more  elements,  then  molecules 
may  be  still  further  divided  into  atoms,  which  accord- 
ing to  Dalton's  theory  are  the  indivisible  particles  of 
which  all  substances  are  composed.  If  we  take  FeO 
as  an  example,  the  smallest  particle  of  FeO  which  can 
exist  is  a  molecule,  and  this  molecule  consists  of  an  Fe 
atom  and  an  0  atom,  which  are  indivisible.  Generally 
atoms  do  not  exist  alone  but  only  in  combination,  that 
is  to  say  an  element  for  example  like  oxygen  consists 
of  molecules  of  oxygen  each  of  which  is  composed  of 
two  atoms  of  oxygen.  We  do  not  have  then  simply  O 
in  the  air  but  O2,  for  when  an  atom  of  O  has  no  Fe  or 
Cu  or  other  element  to  combine  with,  it  unites  with 
another  atom  of  O  making  02. 

The  size  of  an  atom  is  so  small  that  it  cannot  be 
determined  or  even  imagined.  We  know  that  certain 
substances  give  off  odors  for  long  periods  of  time  and 
never  diminish  in  weight.  In  an  attempt  to  convey 
some  idea  as  to  the  size  of  these  minute,  infinitesimal 
particles,  Lord  Kelvin  says:  "Imagine  a  rain  drop 
or  a  globe  of  glass  as  large  as  a  pea,  to  be  magnified  up 


CAN  MATTER  BE  DESTROYED  31 

to  the  size  of  the  earth;  each  constituent  being  magni- 
fied in  the  same  proportion.  The  magnified  structure 
would  be  coarser  grained  than  a  heap  of  small  shot, 
but  probably  less  coarse  grained  than  a  heap  of  cricket 
balls." 

Can  Matter  be  Destroyed? — In  our  experiments  with 
limestone,  we  certainly  changed  this  chemical  com- 
pound and  reduced  its  weight  by  heating.  It  was 
found  that  we  drove  off  a  gas  and  left  a  white  friable 
substance  that  would  unite  with  water  and  in  the 
process  would  still  further  suffer  chemical  and  physical 
changes.  But  we  found  that  after  we  obtained  this 
new  chemical  compound,  hydrated  lime,  we  could 
bubble  the  gases  from  the  kiln  through  it  and  obtain 
not  only  the  same  substance  (limestone)  with  which 
we  started  but  in  exactly  the  same  amount.  In  other 
words  with  careful  handling  no  matter  was  lost.  Con- 
sider another  example:  iron  rusts  and  increases  in 
weight — and  loses  its  metallic  properties.  By  appro- 
priate chemical  processes  we  are  able  to  drive  away 
the  oxygen  and  recover  in  exactly  the  same  amount 
the  metallic  iron.  Well  enough,  but  how  about  the 
burning  of  coal — do  we  not  destroy  the  coal  in  this 
burning  process  which  we  have  learned  to  regard  as 
an  oxidation?  Does  not  the  ash  weigh  less  than 
the  coal  did  ?  The  ash  does  weigh  less,  for  this  repre- 
sents only  the  mineral  parts  of  the  coal.  If  we 
had  taken  the  trouble  to  collect  every  particle  of 
the  gases  given  off  in  this  combustion  (burning)  we 
would  have  found  that  the  weight  of  the  gases  plus 
the  weight  of  the  ash  exceeds  the  weight  of  the 


32  MOLECULES  AND  ATOMS 

coal  and  the  sum  is  exactly  equal  to  the  weight  of 
the  coal  plus  the  weight  of  the  oxygen  used  in  the 
process.  Therefore  nothing  is  destroyed — things  may 
be  changed  physically  and  chemically  and  the  products 
wafted  to  the  four  winds  of  the  earth  but  never  de- 
stroyed. The  ashes  may  be  washed  away  and  the  gases 
dissipated  but  eventually  they  are  gathered  into 
nature's  laboratory  and  rebuilt  into  combustible 
materials.  If  the  elements  were  destroyed  all  our 
methods  of  determining  the  exact  amounts  of  each 
present  in  a  compound  would  be  useless.  The  fact  that 
in  chemical  reactions  there  is  no  change  in  the  weight 
(mass)  of  each  element  is  known  as  the  law  of  the 
conservation  of  mass. 

Energy. — The  woodsman's  method  of  lighting  a  fire 
is  to  rub'  two  pieces  of  wood  together  until  the  heat 
generated  is  sufficient  to  start  the  oxidation  of  the* 
wood.  By  means  of  the  friction  mechanical  energy 
was  transformed  into  heat  and  finally  when  the  heat 
is  present  in  large  quantities  another  form  of  energy, 
namely,  light,  manifests  itself.  Heat  energy  may  be 
transformed  into  mechanical  through  the  agency  of 
the  steam  engine  and  then  into  electrical  energy  by 
the  turning  of  a  dynamo.  Electrical  energy  may  in 
turn  be  transformed  into  light,  mechanical  energy  or 
heat  by  means  of  incandescent  filament,  motor  and 
coils,  respectively. 

Just  as  matter  can  not  be  destroyed  it  is  not  possible 
to  destroy  energy.  Energy  may  be  transformed  into 
heat  and  dissipated  (i.  e.,  lost  to  immediate  surround- 
ings), but  it  always  remains  energy,  and  always  exists 


SUMMARY  OF  CHAPTER  IV  33 

in  the  same  amount.  In  the  transformation  of  the 
energy  contained  in  coal  (latent  energy)  into  steam  or 
electricity  (potential  or  kinetic  energy)  we  may  not 
always  finish  our  experiment  with  the  same  amount 
with  which  we  began  but  this  is  due  to  imperfections 
in  our  machinery.  The  energy  still  exists  somewhere 
either  in  a  latent  or  kinetic  form.  This  is  known  as  the 
principle  of  the  conservation  of  energy. 

SUMMARY  OF  CHAPTER  IV. 

A  compound  is  the  result  of  the  union  of  two  elements. 
The  smallest  unit  of  a  compound  is  a  molecule.  A 
molecule  is  composed  of  atoms.  Iron  oxide,  FeO,  con- 
sists of  very  small  bodies  (molecules)  of  FeO,  which 
in  turn  are  made  up  of  Fe  (atom)  and  0  (atom).  A 
molecule  of  an  element  may  consist  of  one,  two,  three 
or  more  atoms,  a  molecule  of  a  compound  consists  of 
at  least  two  atoms. 

Matter  may  suffer  chemical  or  physical  change 
but  it  cannot  be  destroyed.  In  chemical  reactions 
there  is  no  change  in  the  weight  (mass)  of  the  sub- 
stances involved:  this  is  the  law  of  the  conservation 
of  mass. 

Energy  undergoes  change  in  form  (heat,  light,  elec- 
trical current),  but  is  never  destroyed.  Heat  may  be 
radiated  and  lost  to  immediate  surroundings  but  it 
will  always  exist  as  energy  in  some  form. 


CHAPTER  V. 
CHEMICAL  PROCESSES. 

IN  raising  a  weight  to  a  given  height  a  certain 
amount  of  energy  (kinetic)  is  required.  What  becomes 
of  it — the  weight  isn't  heated  or  lighted  or  electri- 
cally charged  in  the  process.  It  is  simply  stored  up 
as  latent  energy — for  when  that  weight  falls  and 
strikes  it  liberates  exactly  the  same  amount  of  energy 
that  was  required  to  lift  it.  Now,  returning  to  our 
limestone  experiment,  we  will  remember  that  in  driv- 
ing off  the  carbon  dioxide  it  was  necessary  to  use 
heat;  and  when  we  poured  water  on  the  quicklime 
heat  was  liberated.  In  the  first  chemical  process  heat 
was  absorbed  (compare  with  the  raising  of  the  weight), 
in  the  second  heat  was  liberated  (falling  of  the  stone). 
In  every  chemical  process  heat  is  either  absorbed  or 
liberated.  And  we  have  just  come  to  understand  why 
the  water  boils  when  it  is  poured  on  quicklime.  It  means 
that  there  is  a  chemical  union  brought  about  between 
the  quicklime  and  water  with  the  liberation  of  heat. 
When  the  lime  hydrate  is  subjected  to  heat  the  re- 
verse is  true;  that  is,  the  water  is  driven  off  and  heat 
absorbed  in  the  process.  The  amount  of  heat  given 
off  or  absorbed  in  any  chemical  process  is  always  the 
same  for  a  given  mass  of  substances.  Later  we  shall 
learn  that  our  bodies  are  kept  warm  by  the  heat 
which  is  liberated  during  chemical  processes. 


THE  LAW  OF  MULTIPLE  PROPORTIONS       35 

The  Law  of  Constant  Proportions. — If  the  amount  of 
heat  absorbed  or  liberated  is  always  the  same  for  a 
given  mass  of  reacting  substances  as  we  have  just 
learned  then  we  presume  that  these  substances  react 
in  a  constant  ratio  to  one  another.  As  a  matter  of 
fact,  this  observation  simply  confirms  what  had 
already  been  found  out  by  different  methods.  In 
the  early  development  of  chemistry  various  substances 
were  analyzed  in  a  crude  way,  but  the  methods  were 
sufficient  to  detect  the  constancy  with  which  the 
elements  occurred  in  a  given  chemical  substance. 
For  instance,  in  our  lime  experiment  we  started  with 
100  pounds — on  heating  until  constant  weight  was 
attained  we  always  had  56  pounds,  no  more,  no  less, 
provided  we  started  with  100  pounds  of  pure  water- 
free  lime.  It  has  been  found  that  whenever  quicklime 
is  air  slaked,  that  is,  allowed  to  absorb  all  the  carbon 
dioxide  it  will  take  up,  that  the  combining  ratio  is 
always  56  parts  of  quicklime  to  44  parts  carbon  dioxide. 
Many  other  examples  can  be  given  to  prove  that  if 
two  substances  react  chemically  and  form  a  third,  they 
enter  into  combination  in  a  constant  proportion. 

The  Law  of  Multiple  Proportions. — It  has  been  found 
that  two  or  three  elements  may  combine  to  form 
entirely  different  substances.  Methods  for  merely 
detecting  the  presence  of  the  elements  (known  in 
chemistry  as  Qualitative  Analysis)  would  show  no 
difference  between  these  two  compounds,  while  quan- 
titative analysis  (i.  e.}  determining  the  amounts  of  the 
elements  present)  would  bring  out  this  difference  in 
composition.  Two  substances  which  are  used  exten- 


36  CHEMICAL  PROCESSES 

sively  in  medicine  illustrate  this  law.  Calomel,  a 
white  insoluble,  non-crystalline,  non-poisonous  com- 
pound, is  composed  of  one  atom  of  mercury  (quick- 
silver) and  one  atom  of  chlorine  (a  greenish,  pungent 
gas  and  a  constituent  of  common  salt).  The  chemical 
formula  for  mercury-chloride  is  HgCl.  If  instead 
of  one  atom  of  chlorine  combined  with  mercury 
we  have  two,  namely  HgCl2,  an  entirely  different 
chemical  substance  results.  The  latter  substance 
is  bichloride  of  mercury  or  corrosive  sublimate,  a  sol- 
uble, highly  poisonous,  crystalline  compound,  though 
it  contains  nothing  that  is  not  found  in  calomel.  The 
difference  lies  in  the  relative  amounts  of  each.  By 
quantitative  analysis  we  observe  that  the  number  of 
atoms  of  chlorine  in  the  second  compound  is  exactly 
twice  the  number  in  the  first  for  every  atom  of  mer- 
cury. There  are  no  compounds  of  mercury  and  chlorine 
known  in  which  the  number  of  atoms  of  chlorine  is 
one  and  a  half  or  three-quarters,  etc.,  times  the  number 
found  in  calomel.  There  are  only  two  compounds 
of  mercury  and  chlorine  known:  if  no  law  governed 
their  combination  there  would  be  any  number  of 
different  substances  depending  upon  the  relative 
amounts  of  each  present  at  the  beginning  of  the  reac- 
tion. It  has  been  found  that  when  two  elements  com- 
bine in  more  than  one  proportion,  the  masses  of  the  one 
which  combine  with  a  given  mass  of  the  other  bear  a 
simple  rational  relation  to  one  another.  This  ratio  in 
the  mercury  compounds  is  1  to  2.  When  we  come  to 
study  the  oxides  of  iron,  for  example,  we  find  several 
compounds  possible:  FeO,  Fe304,  Fe2O3.  These  com- 


SUMMARY  OF  CHAPTER  V  37 

pounds  may  at  first  glance  seem  at  variance  with 
our  law  and  our  O  seems  to  be  present  in  fractional 
parts,  but  let  us  elevate  them  to  a  common  iron  content 
as  Fe2,  then  our  compounds  become  Fe6O,  Fe6O8  and 
Fe609.  The  combining  ratios  of  the  O  is  6,  8  and  9. 
When  we  come  to  study  the  various  combinations  of 
carbon  and  hydrogen,  we  find  a  wider  application  of 
this  law  because  more  compounds  are  possible:  as 
CH4,  C2H6,  C3H8,  C4H10,  etc. 

The  Law  of  Combining  Weights. — When  chemical 
substances  are  subjected  to  quantitative  analysis,  the 
relative  weights  of  the  elements  entering  into  a  com- 
pound are  found.  To  use  the  mercury  compounds 
as  example,  we  find  that  the  ratio  of  the  weight  of 
mercury  to  the  weight  of  the  chlorine  in  calomel  is 
199.8  to  35.18,  while  in  corrosive  sublimate  the  ratio 
is  199.8  to  70.36.  We  observe  that  the  chlorine  factor 
in  the  second  compound  is  exactly  twice  that  in  the 
first  compound.  After  analysis  of  large  numbers  of 
compounds  the  following  law  has  been  formulated: 
Substances  combine  either  in  the  ratio  of  their  combining 
weights  or  in  simple  multiples  of  these  numbers. 

SUMMARY  OF  CHAPTER  V. 

In  any  given  chemical  reaction,  heat  is  either 
absorbed  or  liberated  in  an  unchangeable  ratio  to  the 
amounts  of  the  substances  reacting.  The  amount  of 
heat  absorbed  when  1  gram  of  lime  is  made  from 
hydrated  lime  is  exactly  the  same  as  that  given  off 
when  water  is  poured  on  1  gram  of  lime. 

If  two  substances  react  chemically  and  form  a  third, 


38  CHEMICAL  PROCESSES 

they  enter  into  combination  in  a  constant  proportion. 
When  two  elements  combine  in  more  than  one  pro- 
portion, the  masses  of  the  one  which  combine  with  a 
given  mass  of  the  other  bear  a  simple  rational  relation 
to  one  another. 

Substances  combine  either  in  the  ratio  of  their  com- 
bining weights  or  in  simple  multiples  of  these  numbers. 


CHAPTER  VI. 
ATOMIC  WEIGHTS. 

THE  gas  used  to  inflate  balloons  is  hydrogen.  This 
colorless,  odorless  gas  is  so  light  in  weight  that  it 
causes  the  balloon  to  float  in  air.  Hydrogen  burns  in 
oxygen  to  form  an  oxide — this  oxide  is  water,  H2O. 
The  gas  chlorine  of  which  we  have  spoken  already  as 
being  able  to  combine  with  mercury  also  combines 
with  hydrogen  to  form  hydrogen  chloride,  HC1.  The 
relative  weights  of  the  combining  substances  are: 
chlorine  35.18  to  hydrogen  1;  that  is,  35.18  grams  of 
chlorine  unite  with  1  gram  of  hydrogen  to  form  36.18 
parts  HC1.  The  substance  iodine,  with  which  we  are 
all  familiar  also  unites  with  hydrogen  to  form  hydrogen 
iodide,  HI,  and  in  the  ratio  of  125.89  I  to  1H.  We 
remember  that  199.8  parts  mercury  unites  with  35.18 
parts  chlorine.  By  continuing  our  analyses  beginning 
with  any  one  element  and  finding  the  ratio  of  the 
combining  weights  of  others,  then  taking  these  and 
working  to  still  others  we  are  able  to  obtain  the  com- 
bining weights  of  all  elements  in  terms  of  one  another. 
Now,  how  should  we  express  them?  The  easiest  way 
is  to  take  the  lightest  element  as  our  basis  and  let  it 
equal  1.  Since  hydrogen  is  the  lightest  element  we  build 
our  system  on  it  stating  that  the  combining  weight  is  1 
and  then  chlorine  will  be  35.18;  iodine  125.89;  mercury 
199.8,  etc.  In  the  hydrogen  chloride  combination  we 


40  ATOMIC  WEIGHTS 

find  one  in  which  the  smallest  quantity  of  hydrogen  has 
entered.  This  1  part  of  hydrogen  must  be  at  least  one 
atom — it  may  be  more  but  it  cannot  be  less.  By  anal- 
yzing large  numbers  of  compounds  and  by  certain  other 
methods  we  arrive  at  the  conclusion  that  one  atom  of 
hydrogen  combines  with  one  atom  of  chlorine.  Since 
the  combining  weights  are  respectively  1  (for  H)  and 
35.18  (for  Cl)  we  say  that  these  numbers  represent 
the  atomic  weights  of  these  elements. 

In  chemical  manipulations  atomic  weights  play  a 
very  important  part  and  if  we  can  simplify  the  system 
of  atomic  weights  to  any  extent  we  save  the  chemist 
that  much.  On  the  basis  of  hydrogen  as  1  nearly  all  the 
atomic  weights  of  the  elements  contain  decimals.  For 
example,  oxygen  when  H=l,  is  15.88.  The  accepted 
system  is  to  let  0  =  16.0  to  make  it  a  round  number, 
then  H  becomes  1.008  and  arsenic  which  was  74.9 
on  the  old  basis  now  becomes  75.0;  phosphorus,  30.96 
becomes  31.0;  mercury  199.8  becomes  200.0.  This 
simplifies  a  great  many  calculations.  It  is  usual  then 
to  state  the  atomic  weight  of  oxygen  as  16,  though 
it  makes  no  difference  which  system  is  used  so  far 
as  the  ultimate  results  are  concerned,  for  all  these 
numbers  are  relative.  If  we  begin  a  calculation  with 
either  system  we  should  of  course  use  it  throughout 
the  immediate  problem. 

Avogadro's  Hypothesis. — If  one  liter  of  hydrogen  and 
one  liter  of  chlorine  are  allowed  to  combine  chemically 
there  results  not  one  liter  of  hydrogen  chloride,  but 
two  liters  of  HC1.  1L.  H  +  1L.  C1.  =  2L.  HC1.  Now 
according  to  Avogadro's  hypothesis  "In  equal  volumes 


MOLECULAR  WEIGHT  41 

of  all  gases,  at  the  same  temperature  and  pressure,  there 
is  an  equal  number  of  molecules."  Therefore,  in  two 
liters  of  HC1  there  must  be  twice  as  many  molecules 
as  there  are  in  one  liter  of  H  or  one  liter  of  Cl  (or  any 
other  gas),  and  since  each  molecule  must  contain  one 
atom  of  H  and  one  atom  of  Cl  it  follows  that  each 
molecule  of  H  and  each  molecule  of  Cl  consists  of 
two  atoms.  Then  hydrogen  as  a  gas  exists  not  as  H 
but  as  H2  and  chlorine  as  C12.  This  is  in  accordance 
with  our  previous  statement  that  when  atoms  of 
elements  have  nothing  else  to  combine  with  they 
sometimes  combine  with  one  another  (see  page  30). 

Molecular  Weight. — The  sum  of  the  atomic  weights 
of  the  elements  composing  a  molecule  is  called  the 
molecular  weight.  For  example,  if  a  molecular  of 
hydrogen  is  H2  and  the  atomic  weight  of  H  =  l,  then 
the  molecular  weight  is  2;  chlorine  exists  as  C12; 
bromine  as  Br2;  nitrogen  as  N2,  etc.,  therefore  the 
molecular  weights  of  these  substances  are  twice  their 
atomic  weights.  Mercury,  however,  exists  as  Hg, 
while  in  phosphorus  there  are  three  atoms  in  a  mole- 
cule, P3.  Further,  in  substances  composed  of  more 
than  one  element  as  HC1,  the  molecular  weight  is  the 
sum  of  the  atomic  weight  of  H  plus  the  atomic  weight 
ofCl,  or  1.008 +35.45  =  36.458  =  molecular  weight  of 
HCL 

Now  for  the  reason  why  we  learn  about  atomic 
weights  and  molecular  weights.  When  chemical  sub- 
stances react  with  one  another,  they  join  atom  to  atom 
not  gram  to  gram.  Obviously,  if  hydrogen  is  the 
lightest  substance  then  a  gram  would  contain  as  many 


42  ATOMIC  WEIGHTS 

more  atoms  as  its  weight  is  less  than  chlorine  for 
instance — so  that  to  obtain  36.458  grams  HC1  we  do 
not  mix  18.229  (one-half  of  36.458)  grams  of  H  with 
the  same  quantity  of  chlorine  but  1.008  gram  H  to 
35.450  Cl.  In  using  gaseous  substances  we  can  measure 
by  volume  but  when  we  come  to  work  with  metals  and 
salts  we  must  weigh  the  materials. 

SUMMARY  OF  CHAPTER  VI. 

The  ratio  of  the  units  of  combining  power  of  elements 
is  spoken  of  as  atomic  weight.  Because  hydrogen  is 
the  lightest  gas  known,  it  is  accepted  as  a  standard 
and  its  atomic  weight  placed,  therefore,  as  1.  Other 
atomic  weights  are  expressed  in  terms  of  hydrogen  as 
1.  The  atomic  weight  of  O  =  15.88  (i.  e.,  15.88  times 
at.  wt.  of  H).  Recorded  in  terms  of  H  many  atomic 
weights  contain  decimals.  To  simplify  calculations  the 
value  of  H  is  placed  at  1.008,  then  at.  wt.  of  O=16.0. 
Other  examples  are  given  in  the  text. 

In  equal  volumes  of  all  gases  at  the  same  temperature 
and  pressure,  there  is  an  equal  number  of  molecules 
(Avogadro's  hypothesis). 

Molecular  weight  is  the  sum  of  the  weights  of  the 
atoms  composing  the  molecule,  e.  g.,  mol.  wt.  of  HC1 
=  at.  wt.  of  H  (1.008)  +  at.  wt.  of  Cl  (35.45)  =  36.458. 
If  the  molecular  weight  of  the  compound  having  the 
empirical  formula  CHO2  is  found  by  physical  measure- 
ments to  be  approximately  90  and  the  sum  of  the 
atomic  weights  is  45  (C  =  12,  H  =  1 .008,  O  =  16)  we  learn 
that  the  real  formula  of  this  compound  is  (CHO2)2 — or 
(COOH)2. 


CHAPTER  VII. 

OXYGEN. 

Occurrence. — It  will  be  remembered  that  our  experi- 
ments already  cited  in  Chapter  II  proved  that  oxygen 
is  one  of  the  chief  constituents  of  the  air.  It  was  also 
stated  that  the  various  metals  occur  in  nature  as  oxides; 
for  example,  ordinary  clay  is  the  oxide  of  aluminum 
and  silicon.  Oxygen  also  exists  in  plant  and  animal 
bodies  and  85  per  cent,  of  the  oceans  of  water  is  oxy- 
gen. Atmospheric  air  contains  23  per  cent,  pure 
oxygen.  So  abundant  is  the  distribution  of  this  ele- 
ment that  it  is  estimated  that  one-half  of  the  earth's 
crust  is  oxygen. 

Preparation  in  the  Laboratory. — Oxygen  in  air  is  mixed 
with  nitrogen,  a  very  inert  (i.  e.,  will  not  combine  easily) 
gas,  and  it  is  therefore  difficult  to  separate  them.  One 
can  decompose  water  by  passing  an  electric  current 
through  it  and  hydrogen  is  given  off  at  the  positive 
electrode  (where  the  current  enters  the  water,  so-called 
anode),  and  oxygen  is  given  off  as  a  gas  at  the  pole 
where  the  current  leaves,  negative  or  cathode,  and  can 
be  collected  in  an  inverted  tube. 

The  heating  of  an  easily  decomposable  oxide  as 
mercury  oxide  is  a  source  of  oxygen: 

2  HgO  =  2Hg  +  O2.     (See  footnote.) 

1  The  Latin  for  mercury  is  hydrargyrum  and  its  abbreviation,  Hg. 
One  will  wonder  why  this  equation  was  not  written  thus:  HgO  = 
Hg  +  O.  In  the  paragraph  on  Avogadro's  hypothesis  and  mole- 


44  OXYGEN 

Commercially  oxygen  is  produced  by  heating  equal 
parts  of  potassium  chlorate  and  manganese  dioxide. 
The  gas  given  off  is  purified  by  washing  in  different 
solutions  and  compressed  into  tanks. 

Uses.— Tubes  or  tanks  of  oxygen  are  found  in  every 
hospital  for  emergency  use  in  cases  of  asphyxiation 
and  where  there  is  small  working  lung  space  as  in  pneu- 
monia or  diminished  breathing  capacity.  Oxygen  is 
necessary  in  nitrous  oxide  anesthesia. 

In  the  arts  oxygen  is  used  with  illuminating  or 
acetylene  gas  to  produce  a  flame  of  intense  heating 
power.  With  such  a  flame  one  can  cut  through  steel 
plate  with  the  greatest  ease. 

Properties  of  Oxygen. — Oxygen  is  a  transparent  gas, 
possessing  neither  color  nor  odor,  and  weighs  one  and 
one-tenth  times  as  much  as  air.  By  diminishing  the 
temperature  to  an  extreme  degree  of  coldness  (below 
— 119°  C.)  and  exerting  very  high  pressure,  oxygen  may 
be  liquefied,  though  with  such  difficulty  that  for  a 
long  time  it  was  considered  impossible. 

The  most  familiar  chemical  phenomenon  is  com- 
bustion which  has  already  been  referred  to  as  oxida- 
tion. It  makes  no  difference  whether  the  reactions 
take  place  quickly  as  the  burning  of  wood,  or  proceeds 
slowly,  as  the  tarnishing  of  silver  or  the  rusting  of  iron, 
the  chemical  process  is  the  same,  namely,  the  chemical 

cules  it  was  stated  that  certain  atoms  combine  with  one  another 
when  they  have  nothing  else  to  combine  with.  This  is  true  of  O, 
that  is,  O  exists  as  C>2  though  mercury  exists  as  Hg.  Then,  so  far  as 
Hg  is  concerned,  this  last  equation  is  possible,  but  if  O  must  combine 
with  something,  it  would  return  to  the  Hg  so  soon  as  it  is  released 
unless  there  is  another  O  present  to  form  Oz.  We  therefore  presume 
that  these  processes  go  in  pairs,  that  is,  2HgO  =  2Hg  +  O». 


OXIDES  45 

union  with  oxygen.  In  pure  oxygen  these  reactions 
take  place  more  easily  than  in  air  which  is  oxygen 
diluted  with  an  inert  gas  (nitrogen).  For  example, 
a  piece  of  phosphorus  exposed  to  the  air  will  take  fire 
spontaneously  and  burn  quietly,  but  if  placed  in  pure 
oxygen,  oxidation  takes  place  immediately  and  with 
explosive  violence.  The  reason  for  this  is  found  in 
the  fact  that  chemical  reactions  proceed  more  rapidly 
as  we  increase  the  temperature.  When  the  gas  is  pure 
oxygen,  all  the  heat  of  the  chemical  reaction  goes  to 
raise  the  temperature  of  the  reacting  substances, 
whereas  in  a  mixture  like  air  a  greater  part  of  the  heat 
is  absorbed  by  a  non-reacting  substance  (nitrogen). 

Oxides. — When  an  element  burns  or  is  slowly  acted 
upon  by  oxygen  an  oxide  is  formed.  Certain  elements 
are  capable  of  combining  with  oxygen  in  different 
proportions  forming  totally  different  compounds.  By 
burning  carbon  in  various  amounts  of  air,  we  are  able 
to  produce  a  compound  containing  1  part  of  oxygen 
for  every  carbon  atom  and  also  to  prepare  an  oxide 
containing  two  parts  of  oxygen  for  every  carbon  atom. 
If  there  is  an  excess  of  carbon  and  very  little  air  the 
former  oxide  (CO)  called  carbon  monoxide,  results, 
while  with  abundant  air  supply  carbon  dioxide  (CO2)  is 
produced.  Carbon  monoxide  is  a  deadly  poisonous 
gas  while  carbon  dioxide  is  relatively  harmless. 

Thus  the  oxides  are  named  first  according  to  the 
number  of  atoms  of  oxygen  present  as  monoxide,  dioxide, 
trioxide,  pentoxide,  etc.  Where  the  number  of  atoms  of 
the  element  in  combination  with  the  oxygen  may  also  be 
different  we  use  "oits"  and  "I'c"  to  indicate  oxides 


46  OXYGEN 

poorer  or  richer  in  oxygen.  FeO  is  called  ferrous 
oxide,  while  Fe2O3  is  ferric  oxide — an  -ous  oxide  con- 
tains less  oxygen  while  -ic  oxides  contain  more.  We 
shall  find  that  this  same  terminology  is  applied  to  other 
compounds  like  the  chlorides,  iodides,  sulphides,  etc. 

Ozone. — The  peculiar  pungent  odor  noticeable  in 
the  neighborhood  of  electrical  dynamos  and  x-ray 
apparatus  is  due  in  part  to  the  presence  of  ozone  in 
the  air.  It  is  best  produced  by  passing  a  silent  dis- 
charge of  electricity  through  pure  oxygen.  Ozone  is  a 
very  active  oxidizing  agent  and  for  this  reason  is  a 
very  efficient  deodorizer  and  disinfectant.  It  is  used 
to  rid  municipal  water  supplies  of  bacteria  by  allowing 
the  water  to  fall  from  a  tower  while  ozone  is  bubbled 
through  it. 

A  few  hospitals  in  America  use  ozone  to  sterilize 
their  operating  room  supplies.  Metallic  silver  when 
placed  in  an  atmosphere  of  ozone  at  ordinary  tempera- 
ture will  be  covered  with  a  layer  of  brown  oxide;  while 
oxygen  under  similar  conditions  will  not  bring  about 
such  an  oxidation.  By  heating  to  300°  C.  ozone  is 
changed  to  oxygen — which  in  turn  may  be  retrans- 
formed  to  ozone  by  an  electric  current.  On  account 
of  this  and  other  facts  it  is  believed  that  ozone  is  oxygen 
plus  an  extra  amount  of  energy  and  instead  of  existing 
as  02  (oxygen  gas)  is  Os. 

SUMMARY  OF  CHAPTER  VII. 

Oxygen  is  a  transparent  gas  possessing  neither  color 
nor  odor.  It  is  slightly  heavier  than  air  and  can  be 
liquefied.  Oxygen  is  necessary  for  life.  It  is  very 


SUMMARY  OF  CHAPTER  VII  47 

widely  distributed  in  nature  (about  half  the  crust 
of  the  earth  is  said  to  be  oxygen  bound  to  metals  and 
other  elements  forming  oxides).  Combustion  is  an 
oxidizing  process,  that  is,  the  union  of  oxygen  with 
any  substance.  Oxidation  may  proceed  rapidly  with 
the  product  of  light  and  heat  (fire)  or  very  slowly 
in  water  solution  (life  processes). 

Oxygen  may  be  prepared  by  decomposing  water 
with  an  electric  current  or  by  heating  mercury  oxide. 

Ozone  is  a  pungent  gas  product  by  electric  sparks 
in  oxygen.  There  are  reasons  for  the  belief  that  ozone 
is  oxygen  plus  energy  and  that  the  molecule  of  oxygen 
gas  contains  two  atoms  (O-2)  while  the  ozone  molecule 
contains  three  atoms  (O3).  Ozone  is  used  to  sterilize 
water  supplies  and  as  an  oxidizing  agent  in  the  labora- 
tory. Ozone  is  also  an  efficient  deodorizer. 


CHAPTER  VIII. 
HYDROGEN,  H2. 

(Mol.  wt.  =  2.016;  At.  wt.  =  1.008.) 

Occurrence. — Very  small  quantities  of  hydrogen 
occur  in  the  atmosphere  of  the  earth  but  by  spectrum 
analysis  it  has  been  discovered  to  be  very  widely  dis- 
tributed in  the  stars,  the  sun,  and  is  found  in  nebulous 
masses.  Deposits  of  free  hydrogen  have  been  found 
in  great  salt  deposits  and  in  oil  wells.  Eleven  per  cent, 
of  water  is  hydrogen,  so  that  in  actual  amounts  it  ranks 
next  to  oxygen  in  the  earth's  composition. 

Preparation  in  the  Laboratory. — Just  as  oxygen  is 
given  off  at  the  positive  pole  when  an  electric  current 
is  passed  through  water,  hydrogen  the  only  other  com- 
ponent is  given  off  at  the  negative1  electrode  and  may 
be  collected  in  the  closed  end  of  a  tube. 

The  practical  method  of  producing  hydrogen  is  to 


1  Since  positively  charged  substances  attract  negatively  charged 
substances  and  vice  versa  we  assume  that  oxygen  is  a  negatively 
charged  substance  because  it  is  attracted  to  the  positive  pole  and  that 
hydrogen  is  positively  charged  because  it  is  attracted  to  the  negative 
pole.  We  shall  later  learn  that  the  metals  (iron,  copper,  silver, 
nickel,  sodium  potassium,  etc.)  are  like  hydrogen  in  being  classed  sa 
positive  elements,  while  chlorine,  bromine,  iodine,  sulphur,  fluorine 
can  be  classed  as  negative  as  a  general  rule  and  that  one  of  the  positive 
elements  will  easily  combine  with  a  negative  element.  Some  elements 
as  arsenic  and  phosphorus  combine  easily  with  either  oxygen  or 
hydrogen  but  to  attempt  to  explain  this  would  take  us  into  physical 
chemistry. 


PROPERTIES  OF  HYDROGEN  49 

allow  hydrochloric  acid  (the  acid  which  is  normally 
present  in  the  stomach)  to  act  on  a  metal  like  zinc: 

Zn  +  2HC1  =  Zn  C12  +  H2. 

Uses. — Hydrogen  is  compressed  into  tanks.  It 
burns  with  an  intense  non-luminous  flame  and  hence 
is  used  in  welding  and  heating  processes.  With  a 
hydrogen-oxygen  blow-pipe  cast  iron  can  be  welded. 
Balloons  are  inflated  with  hydrogen  because  it  is  lighter 
than  air.  In  the  laboratory  hydrogen  is  used  as  a 
reducing  agent,  that  is,  used  to  combine  with  the  oxygen 
held  in  combination  by  some  other  substance  and  thus 
de-oxidize.  In  this  case  it  is,  as  a  rule,  generated  in 
contact  with  the  substance  to  be  reduced  for  it  is  more 
active  just  at  the  point  of  liberation  when  it  is  said  to 
be  nascent  (born).1  In  the  bacteriological  laboratory 
hydrogen  is  used  to  displace  the  oxygen  of  the  air 
when  it  is  desirable  to  cultivate  organisms  which  will 
not  grow  in  the  presence  of  oxygen. 

Properties  of  Hydrogen. — Hydrogen  is  a  transparent 
gas  possessing  neither  color  nor  odor  and  is  the  lightest 
of  all  known  substances.  It  can  be  liquefied  with 
difficulty  by  diminishing  the  temperature  to  —200° 
under  a  pressure  of  three  hundred  atmospheres  and 
allowing  it  to  expand  into  a  pressure  of  about  fifty 
atmospheres  when  the  heat  absorbed  during  the  process 
of  expansion  will  still  further  cool  it  until  it  liquefies. 
If  liquid  hydrogen  is  poured  into  a  test-tube  liquid 
air  will  flow  from  the  outside  and  finally  the  tube  will 
be  covered  with  frozen  air. 

1  The  H  atoms  are  liberated  and  seek  to  combine  with  oxygen 
before  combining  with  another  H  to  form  Hz, 
4 


50  HYDROGEN 

Hydrogen  combines  with  chlorine,  iodine,  bromine 
to  form  acids,  in  fact  hydrogen  is  present  in,  and  is  a 
necessary  constituent  of,  all  acids.  In  combination  with 
nitrogen,  hydrogen  forms  ammonia  (NH3)  and  with 
carbon  forms  a  long  series  of  so-called  organic  com- 
pounds. Hydrogen  combines  readily  with  sulphur 
to  form  the  bad-smelling  gas  hydrogen  sulphide  H2S, 
and  with  palladium  and  sodium,  etc.,  to  form  hydrides, 
Pd2H,  NaH. 

Hydrogen  seems  to  possess  a  special  affinity  for 
oxygen.  If  these  two  gases  are  mixed  in  the  ratio 
of  two  parts  of  hydrogen  to  one  of  oxygen  they  form 
a  highly  explosive  mixture  which  can  be  easily  set  off 
by  a  flame.  This  fact  should  be  remembered  when 
working  with  hydrogen  gas. 

When  hydrogen  gas  is  passed  over  an  oxide  of  a 
metal  such  as  iron  at  high  temperatures,  the  hydrogen 
combines  with  the  oxygen  to  form  water  as  in  the 
following  equation: 

Fe3O4  +  4H2  =  4H2O  +  3Fe. 

If  water  vapor  is  passed  over  heated  iron  the  reverse 
is  true: 

4H2O  +  3Fe  =  Fe3O4  +  4H2. 

How  then  are  we  going  to  know  what  will  happen? 
It  has  been  found  that  if  hydrogen  is  present  in  excess 
metallic  iron  will  result,  but  if  water  vapor  is  present 
in  excess  the  oxide  of  iron  is  formed. 

This  illustrates  the  effect  of  quantity  (mass)  on 
chemical  reactions  and  the  reaction  here  given  is  said 
to  be  reversible  in  that  it  may  proceed  either  way 


SUMMARY  OF  CHAPTER  VIII  51 

according  to  the  quantity  of  materials  present.  To 
indicate  the  reversibility  of  chemical  reaction  the 
equation  may  be  written  thus: 

3Fe  +  4H2O  ^  Fe3O4  +  4H2O. 

Most   chemical   reactions   are   reversible. 

SUMMARY  OF  CHAPTER  VIII. 

Hydrogen  is  an  element.  It  is  a  transparent,  colorless, 
odorless  gas  and  the  lightest  of  all  known  substances. 
It  can  be  liquefied.  Hydrogen  combines  with  chlorine, 
iodine,  bromine,  etc.,  to  form  acids;  it  unites  with 
metals  to  form  hydrides,  and  with  carbon  and  oxygen 
to  form  a  long  list  of  organic  compounds.  It  unites 
with  nitrogen  to  form  ammonia  (NH3)  and  with 
oxygen  to  form  water  (H2O). 

Just  as  the  addition  of  oxygen  to  a  substance  is 
called  oxidation  the  addition  of  hydrogen  is  called 
reduction.  When  hydrogen  is  added  to  a  substance 
containing  oxygen,  the  hydrogen  and  oxygen  unite  to 
form  water  and  split  off  from  the  molecule  of  the  sub- 
stance— so  that  reduction  may  mean  the  abstraction  of 
oxygen  by  hydrogen.  If  no  oxygen  is  present  reduction 
means  simply  the  addition  of  hydrogen  to  the  molecule. 

Hydrogen  occurs  in  small  quantities  in  the  at- 
mosphere and  free  in  the  earth's  crust.  It  is  present 
in  large  amounts  in  combination:  water  is  11  per  cent, 
hydrogen  (by  weight). 

Hydrogen  results  from  the  decomposition  of  water 
by  an  electric  current.  The  volume  of  the  hydrogen 
given  off  at  the  negative  pole  is  twice  the  volume  of  the 


52  HYDROGEN 

oxygen  given  off  at  the  positive  pole.  Hydrogen  is 
said  to  be  positive  because  it  is  attracted  to  the  negative 
pole. 

Hydrogen  is  also  prepared  by  the  action  of  HC1 
on  zinc. 

Hydrogen  is  used  in  balloons  (on  account  of  its  light- 
ness) and  in  chemistry  for  reduction.  It  is  used  to 
replace  oxygen  in  certain  bacteriological  methods. 


CHAPTER  IX. 
WATER,  H2O. 

(Mol.  wt.  =  18.) 

WHEN  pure  hydrogen  or  any  compound  containing 
hydrogen  is  burned  in  oxygen  or  air,  water  results. 
If  a  cold  object  is  held  above  a  flame  water  condenses 
on  it.  This  is  true  if  the  flame  consists  of  burning 
gas  which  has  been  deprived  of  all  water  vapor,  so  it 
follows  that  water  is  one  of  the  end-products  of  com- 
bustion. 

Occurrence. — By  far  the  commonest  chemical  com- 
pound is  water.  Widely  distributed  as  it  is  over  and 
through  the  earth's  crust,  the  chief  constituent  of 
animal  and  vegetable  matter,  it  is  so  common  and  so 
familiar  that  we  accept  it  without  inquiry  as  to  its 
composition.  Not  until  we  begin  the  study  of  chemistry 
do  we  wonder  what  its  makeup  is,  and  since  chemistry 
can  tell  us  about  such  common  things  this  science  no 
longer  seems  artificial  and  set  apart  from  every-day 
things.  From  now  on  we  shall  look  upon  water, 
salt,  wood,  rocks  and  coal  in  a  new  light — that  is,  from 
the  stand-point  of  their  chemical  composition. 

Three-fourths  of  the  earth's  surface  is  covered  with 
water,  70  per  cent,  of  our  bodies  is  water,  and  stones 
which  seem  to  be  dry  contain  an  astonishingly  large 
amount  of  it.  Without  it  the  earth  would  be  dead. 


54  WATER 

Uses.— The  great  solvent  for  chemical  substances  is 
water.  Without  it  many  chemical  substances  will  not 
react;  for  example,  an  explosive  mixture  of  hydrogen 
and  oxygen  will  not  explode  if  both  gases  are  perfectly 
dry;  hydrogen  and  chlorine  will  remain  forever  un- 
combined  if  mixed  in  an  absolutely  dry  state.  All 
chemical  processes  of  living  matter,  plant  and  animal, 
take  place  in  the  presence  of  water.  Digestion,  assimi- 
lation, oxidation  and  elimination  require  water  and  by 
the  aid  of  it  heat  regulation  of  the  body  is  possible. 
The  decompositions  of  plants  and  animals  by  which 
the  elements  are  liberated  to  be  reformed  into  living 
matter  require  moisture,  since  these  processes  are 
carried  out  by  bacteria  and  their  ferments  which 
cannot  work  in  the  absence  of  water.  Water  is  the 
great  cleanser  and  heat  regulator  of  the  earth. 

Properties. — The  physical  properties  of  water  are 
so  well  known  that  it  is  not  necessary  to  review  them 
here.  It  is  wise,  however,  to  discuss  certain  facts 
concerning  such  a  common  substance  in  order  that 
other  less  common  substances  and  their  forms  may  be 
compared  with  it.  On  account  of  the  fact  that  water 
is  so  easily  obtained  in  a  pure  condition,  it  is  used  as  a 
standard  of  comparison. 

The  scientific  standard  of  distance  is  the  meter 
(about  39  inches). 

One-hundredth  of  a  meter  is  called  a  centimeter. 
The  volume  of  a  perfect  cube  which  measures  exactly 
1  cm.  on  every  side  is  1  c.c.;  in  other  words,  the 
amount  of  liquid  which  a  cubic  container  measuring 
inside  1  cm.  each  way  is  1  c.c.  From  this  measurement 


HYDROMETER  55 

of  distance  we  obtain  standards  for  weight  measure 
by  using  pure  water.  At  15°  centigrade  1  c.c.  of  water 
weighs  exactly  1  gram,  which  is  the  standard  for 
weight  measure.  (See  Weights  and  Measures,  p.  24.) 

Specific  Gravity. — (Sp.  gr.)  Specific  Gravity  means 
particular  weight.  It  is  a  well  known  fact  that  a  gallon 
of  molasses  weighs  more  than  a  gallon  of  water,  that  is, 
volume  for  volume  molasses  is  heavier  than  water. 
If  1  c.c.  of  molasses  wreighs  1.5  gram  and  1  c.c.  pure 
water  weighs  1  gram  then  obviously  volume  for 
volume  molasses  is  one  and  one-half  times  as  heavy 
as  water,  or  accepting  water  as  the  standard  of  com- 
parison with  specific  gravity  as  1.000  then  the  specific 
gravity  of  molasses  is  1.500. 

Molasses  is  a  solution  of  sugars  in  water  with  some 
caramel  and  extractions  which  add  to  the  color  and 
flavor.  The  more  sugars  dissolved  in  a  given  volume 
of  water  the  greater  the  specific  gravity.  When  we 
come  to  study  the  chemistry  of  the  urine,  we  shall 
see  that  the  determination  of  specific  gravity  is  very 
important  for  the  reason  that  we  are  able  to  ascertain 
by  a  very  quick  and  simple  process  the  amount  of  solids 
in  the  urine.  The  salts  and  nitrogen-containing  bodies 
dissolved  in  it  make  its  specific  gravity  vary  from 
1 .020  to  1 .030.  High  specific  gravity  leads  us  to  suspect 
the  presence  of  sugar  in  urine. 

Hydrometer. — The  instrument  for  quick  determination 
of  the  specific  gravity  of  liquids  consists  of  a  glass 
bulb  filled  with  air  and  weighted  with  mercury  so  that 
the  1.000  mark  on  the  graduated  stem  is  exactly  at 
the  surface  when  the  instrument  floats  in  pure  water. 


56  WATER 

It  is  called  the  hydrometer  (water-measure) .  See  chapter 
on  Uranalysis. 

Lighter  Liquids. — Ether  floats  on  water  and  is  there- 
fore lighter  than  water.  1  c.c.  weights  only  0.717 
gram:  its  specific  gravity  is  0.717.  Pure  alcohol  has 
a  specific  gravity  of  0.797,  but  when  water  is  added 
its  specific  gravity  is  proportionally  increased.  By 
determining  the  specific  gravity  of  a  sample  of  alcohol 
one  can  ascertain  how  much  water  has  been  added. 
Kerosene  and  gasoline  are  obtained  from  the  same 
source,  both  are  lighter  than  water,  but  gasoline  has 
the  lower  specific  gravity.  These  two  liquids  are  sold 
on  the  basis  of  their  specific  gravity.  If  the  specific 
gravity  of  kerosene  is  low,  it  indicates  that  it  contains 
too  much  gasoline  and  is  therefore  dangerous  for  use 
in  lamps,  and  if  the  specific  gravity  of  gasoline  is  too 
high  it  is  not  fit  for  motors.  We  see  that  the  determina- 
tion of  specific  gravity  has  a  very  practical  bearing, 
since  we  may  employ  it  in  determining  the  relative 
purity  of  certain  liquids. 

Thermometer. — The  freezing-  and  the  boiling-point  of 
pure  water  are  the  constants  upon  which  the  standard 
chemical  thermometer  is  made.  As  the  name  (Centi- 
grade, 100°)  indicates  the  difference  between  the  boiling- 
point  and  the  freezing-point  is  divided  into  one  hundred 
parts  and  each  part  called  a  degree.  Then  water  boils 
at  100°  C.  and  freezes  at  0°  C.  The  only  other  kind 
of  thermometer  with  which  nurses  must  be  familiar 
is  the  Fahrenheit,  named  after  its  inventor.  Water 
boils  at  212°  F.  and  freezes  at  32°  F.  The  difference 
between  the  two  is  180°  F.,  and  it  follows  that,  since 


BOILING-POINT  57 

100°  Centigrade  covers  the  same  range  as  180°  F., 
1°  C.  =  1.8°  F.  If  we  wish  to  convert  Centigrade  to 
Fahrenheit  we  multiply  by  1.8  and  add  32  (because 
in  Centigrade  we  begin  at  freezing-point),  which  equals 
0.37°  C.,  means  37°  C.  above  freezing-point,  whereas 
if  37°  C.  equals  in  range  66.4°  F.  we  must  take  it  to 
mean  66.4°  above  the  freezing-point  of  water.  Since 
32°  F.  is  freezing-point  of  water,  66.4°  above  this 
point  is  66.4+32.0  =  98.4.  Therefore  37°  C.  =  98.4°  F.1 

To  convert  Fahrenheit  reading  to  Centigrade  we 
subtract  32  and  divide  by  1.8.2 

Boiling-point. — It  has  been  stated  that  the  boiling- 
point  of  pure  water  is  100°  C.  This  is  true  at  sea  level, 
but  if  we  go  up  a  mountain  we  find  that  the  boiling- 
point  gradually  becomes  less  and  less.  On  the  top  of 
Mont  Blanc  the  boiling-point  is  sometimes  as  low  as 
84°.  The  reason  for  this  lowering  is  the  decrease  in 
atmospheric  pressure.  The  same  result  may  be  ac- 
complished in  the  laboratory  by  reducing  the  atmos- 
pheric pressure  by  means  of  a  vacuum  pump.  Knowing 
the  boiling-point  of  water  at  any  place  we  are  able  to 
estimate  roughly  the  height  above  sea  level. 

If,  on  the  other  hand,  we  increase  the  pressure  on 
the  surface  of  the  water  the  boiling-point  is  corre- 
spondingly raised.  This  is  what  happens  in  a  steam 
boiler  or  steam  sterilizer.  In  the  latter  instead -of  a 

1  37°  C.  or  98.4°  F.  is  the  normal  temperature  of  the  human  body. 

2  Since  the  Centigrade  thermometer  is  being  used  more  and  more 
in  clinical  work,  and  since  the  confusion  of  the  two  systems  in  carrying 
out  orders  might  at  times  be  dangerous,  it  is  suggested  that  the  pupil 
nurses  convert  several  readings,  one  into  the  other.     Room  tempera- 
ture 68°  F.  (20°  C.),  normal  body  temperature  and  bath  tempera- 
tures are  good  points  to  fix  in  their  minds. 


58  WATER 

temperature  of  212°  F.,  we  reach  225°  F.;  but  the 
pressure  is  also  increased  to  about  15  pounds  per  square 
inch.  On  account  of  being  able  to  increase  the  tem- 
perature above  the  sea-level  boiling-point  we  are 
enabled  to  kill  many  bacteria  not  killed  by  boiling. 

SUMMARY  OF  CHAPTER  IX. 

Water  is  composed  of  two  volumes  of  hydrogen  and 
one  volume  of  oxygen  (H2O).  By  weight  11  per  cent, 
of  water  is  hydrogen  and  89  per  cent,  oxygen. 

When  hydrogen  or  any  compound  containing  hy- 
drogen is  burned  in  air  (or  oxygen)  water  is  one  of 
the  products  of  combustion. 

Water  is  necessary  for  life  and  for  many  chemical 
reactions.  It  is  the  great  chemical  solvent. 

Water  is  very  widely  distributed  in  nature.  It  can 
be  easily  obtained  in  a  pure  state,  and  is  therefore 
used  as  a  standard  of  comparison  for  various  physical 
characteristics.  The  relative  weight  of  a  given  volume 
of  any  substance  compared  with  an  equal  volume  of 
water  is  spoken  of  as  the  specific  gravity  of  a  substance. 
The  specific  gravity  of  water  is  taken  as  1.0. 

The  standard  unit  of  volume  is  the  cubic  centimeter. 
1  c.c.  weighs  1  gram  at  15°  C. 

The  instrument  for  measuring  the  specific  gravity 
of  liquids  is  the  hydrometer. 

The  thermometer  registers  the  degree  of  heat.  There 
are  several  kinds;  especial  mention  is  made  of  the 
Fahrenheit  and  the  Centigrade.  Water  freezes  at 
0°  C.  or  32°  F.  Water  boils  at  100°  C.  or  212°  F. 
To  convert  Centigrade  reading  to  Fahrenheit  multiply 


SUMMARY  OF  CHAPTER  IX  59 

by  f  (or  1.8)  and  add  32.  To  convert  Fahrenheit 
readings  to  Centigrade  subtract  32  and  either  multiply 
by  f  (or  0.555)  or  divide  by  1.8. 

Boiling-points  of  liquids  decrease  with  a  decrease 
in  pressure  and  vice  versa.  Water  boils  below  100°  C. 
(212°  F.)  on  top  of  mountains. 


CHAPTER  X. 
HEAT. 

Heat  Absorbed  in  Evaporation. — The  thermometer 
measures  the  degree  of  heat  not  the  amount  of  heat. 
Obviously  it  requires  a  larger  amount  of  heat  to  raise 
a  gallon  of  water  1°  than  it  takes  to  raise  the  tempera- 
ture of  a  quart  of  water  1°.  Just  as  we  have  liquid 
measures  and  standards  of  weight  we  accept  an  easy 
and  simple  standard  for  measuring  heat.  The  standard 
unit  is  the  Calorie1  (large  Calorie)  which  is  the  heat 
required  to  raise  the  temperature  of  1000  grams  of 
pure  water  1°  C.  One  thousand  grams  (1  kilogram)  of 
water  equals  1000  c.c.  or  1  liter  and  is  approximately 
one  quart,  so  that  a  Calorie  is  approximately  the 
amount  of  heat  necessary  to  raise  the  temperature  of  a 
quart  of  water  1°  C.  or  1.8°  F. 

To  raise  the  temperature  of  one  quart  of  water  from 
room  temperature  (20°  C.)  to  the  boiling-point  (100°  C.) 
about  80  Calories  is  needed.  Now  in  order  to  convert 
this  amount  of  water  at  100°  C.  into  steam  at  100°  C. 
a  great  amount  of  heat  is  necessary,  viz.,  540  Calories. 
This  heat  necessary  to  change  a  substance  from  a 
liquid  to  a  gaseous  state  is  known  as  the  heat  of  vaporiza- 
tion. The  heat  of  vaporization  is  absorbed  by  the 
steam  and  given  out  again  on  condensation.  The  heat 

1  The  small  Calorie  is  the  heat  required  to  raise  the  temperature 
of  1  gram  water  1  °  C. 


THE  FREEZING  OF  WATER  61 

of  vaporization  interests  us  on  account  of  the  fact 
that  nature  makes  use  of  it  in  the  cooling  of  the  human 
body;  sweat  is  secreted  upon  the  skin  by  the  sweat 
glands  and  the  large  amount  of  heat  absorbed  during 
vaporization  lowers  the  temperature  of  the  body. 

The  definition  of  the  term  Calorie  should  be  remem- 
bered, for  use  will  be  made  of  it  later  in  the  discussion 
of  food  values. 

The  Freezing  of  Water. — The  well  known  principle: 
heat  expands,  cold  contracts,  holds  good  for  water 
between  certain  limits.  On  being  heated  water  ex- 
pands slightly  and  when  the  same  mass  occupies 
more  volume  the  density  or  specific  gravity  becomes 
less.  For  this  reason  specific  gravity  determinations 
and  accurate  measurements  of  water  must,  be  made 
at  an  accepted  temperature — say  15°  C.,  in  order  to  be 
comparable.1 

The  differences  in  density  thus  produced  cause  up 
and  down  currents  in  bodies  of  water.2 

Water  becomes  denser  on  cooling  until  the  tem- 
perature of  4°  C.  is  reached  and  between  4°  and  0° 
it  expands,  so  that  when  it  freezes  the  ice  produced  is 
lighter  than  water  and  will  float.  If  water  continued 

1  Sometimes  determinations  of  specific  gravity  are  made  at  25° 
C.  based  on  the  density  of  water  at  25°  C.,  then  the  result  of  such  a 
determination  of  specific  gravity  of,  let  us  say,  a  sample  of  urine 
would  be  expressed  thus:  Sp.  gr.  25°/25°  =  1.0236.     This  means  that 
the  sample  of  urine  at  25°  C.  is  1.0236  times  as  heavy  as  water  at 
25°  C. 

2  In  the  spring  and  autumn  one  often  notices  a  peculiar  fishy, 
violet,  or  aromatic  odor  in  tap  water.     This  is  due  to  the  stirring 
up  of  algse  by  the  spring  or  autumn  turn-over.     These  turn-overs 
result  from  the  difference  in  density  of  the  top  and  bottom  layers 
of   bodies  of  water — the  top   cooling,    thus   becoming  more   dense 
settles  while  the  bottom  layer  comes  up. 


62  HEAT 

to  contract  to  0°  ice  would  form  and  sink  to  the  bottom. 
Streams  and  lakes  would  freeze  throughout. 

Heat  Absorbed  in  Melting. — Ice  at  0°  cannot  change 
to  water  at  0°  without  absorbing  a  relatively  large 
amount  of  heat.  The  amount  of  heat  absorbed  by 
one  kilogram  of  ice  (2.2  Ibs.)  in  changing  to  water 
is  about  80  Calories,  or,  the  amount  of  heat  abstracted 
from  a  liter  (about  1  quart)  of  water  in  being  cooled 
from  80°  C.  to  zero.  Ordinary  room  temperature  is 
from  20°  to  25°  C.,  and  refrigerator  temperature 
varies  from  4°  C,  to  14°  C.,  a  difference  of,  let  us  say, 
10°  C.  Then  one  kilogram  of  ice  in  melting  would 
absorb  enough  heat  to  cool  over  8  quarts  of  water 
from  room  temperature  to  refrigerator  temperature. 

Freezing  Mixture. — When  ice  is  placed  in  water  ice 
melts  and  cools  the  water  until  there  is  an  equilibrium 
established  between  the  solid  and  liquid  forms  of  water 
at  0°  C.  When  more  heat  is  absorbed  more  ice  goes 
into  the  liquid  form  and  the  temperature  is  lowered. 
If  one  adds  salt  to  ice  or  the  water-ice  mixture  it  has  a 
tendency  to  make  more  ice  melt,  and  when  ice  melts 
it  absorbs  heat;  therefore  the  water-ice-salt  mixture 
becomes  colder.  If  an  excess  of  ice  and  an  excess  of 
salt  be  present  a  constant  temperature  of  — 18°  C. 
(18°  C.  below  freezing  point)  is  maintained.  If  the 
temperature  is  higher  than  — 18°  C.  more  salt  goes  into 
solution  and  melts  more  ice  which  absorbs  heat  until 
the  constant  point  (  —  18°)  is  reached.  If  the  mixture 
cools  lower  than  — 18°  salt  crystallizes  out  of  solution 
and  allows  ice  to  form  until  the  temperature  is  raised 
to  a  constant  point. 


SUMMARY  OF  CHAPTER  X  63 

The  reason  for  these  facts  cannot  be  explained 
without  going  into  physical  chemistry  but  the  applica- 
tion can  be  readily  seen.  This  is  the  method  used  in 
making  ice-cream  or  for  cooling  anything  quickly. 
The  essential  thing  in  making  such  a  freezing  mixture 
is  to  always  have  present  an  excess  of  salt  and  an  excess 
of  ice.  It  should  be  remembered  that  —18°  C.  is 
intense  cold  and  that  such  a  mixture  should  not  there- 
fore be  used  in  an  ice-bag  applied  to  a  patient. 

SUMMARY  OF  CHAPTER  X. 

The  thermometer  registers  the  degree  of  heat.  The 
quantity  of  heat  is  expressed  in  Calories.  A  small 
Calorie  is  the  amount  of  heat  necessary  to  raise  the 
temperature  of  one  gram  of  water  1°  C.  The  large 
Calorie  (C)  equals  1000  small  Calories.  The  large 
Calorie  is  generally  used. 

The  heat  necessary  to  change  a  substance  from  a 
liquid  to  a  gaseous  state  (water  at  100°  C.  into  steam 
at  100°  C.)  is  known  as  the  heat  of  vaporization. 

Heat  of  vaporization  is  exactly  equal  to  heat  of 
condensation. 

One  kilogram  of  ice  at  0°  C.  absorbs  80  Calories  in 
changing  to  water  at  0°  C. 

Heat  of  freezing  is  exactly  equal  to  heat  of  melting. 

A  mixture  of  ice-salt-water  will  maintain  a  tempera- 
ture of  —18°  C.  so  long  as  ice  and  salt  are  present  in 
excess. 


CHAPTER  XL 

SOLUTIONS  AND  PURIFICATION  OF 
SUBSTANCES. 

SOLUTIONS. 

WATER  is  the  most  important  solvent.  According 
to  Jones'  Inorganic  Chemistry  over  three-fourths  of 
the  chemical  reactions  with  which  we  are  familiar  take 
place  in  water  solution;  certainly  the  reactions  which 
take  place  in  nature  proceed  in  aqueous  solutions. 

Nearly  all  substances — solids,  liquids  and  gases — 
are  soluble  to  a  greater  or  less  degree  in  water.  Many 
things  are  regarded  in  a  practical  sense  as  being  in- 
soluble in  water,  which  are  so  slightly  soluble  as  to  be 
negligible,  nevertheless  possess  a'  definite  degree  of 
solubility.  We  are  familiar  with  the  solution  of  solid 
things  in  a  liquid  but,  perhaps,  we  have  not  thought  of 
the  insolubility  of  liquids.  Alcohol  and  water  are  mis- 
cible  in  all  proportions,  that  is,  the  one  has  unlimited 
solubility  for  the  other;  but  chloroform  and  water  will 
not  mix  in  all  proportions.  Pour  some  chloroform  into 
water  and  it  sinks  to  the  bottom.  Shake  them  and  the 
chloroform  is  emulsified  but  soon  collects  again  at  the 
bottom  of  the  vessels  but  in  a  smaller  amount.  The 
water  if  poured  off  will  retain  a  definite  amount  of 
chloroform  and  has  acquired  a  sweetish  taste  and  an 
odor  characteristic  of  chloroform.  This  is  the  way 


EFFECT  OF  TEMPERATURE  ON  SOLUBILITY     65 

chloroform  liniment  is  prepared.  By  determining  the 
specific  gravity  of  the  solution  we  find  that  it  is  greater 
than  1,  and  knowing  the  specific  gravity  of  chloroform 
we  calculate  using  the  exact  figures  found,  the  exact 
amount  of  chloroform  dissolved. 

Gases  are  soluble  in  water  according  to  the  pressure 
of  that  particular  gas  on  the  surface  of  the  liquid. 
The  presence  of  other  gases  creating  an  enormous 
pressure  would  have  no  effect  on  this. 

Heat  some  water  from  the  tap  in  a  glass  beaker  and 
observe  the  bubbles  coming  off  long  before  the  water 
reaches  the  boiling  point.  This  is  the  dissolved  air 
being  driven  off.  Taste  some  water  which  has  been 
recently  boiled  and  observe  its  flatness.  Agitate  it 
with  air  and  it  regains  its  normal  taste. 

Effect  of  Temperature  on  Solubility. — The  general 
effect  of  raising  the  temperature  of  the  solvent  is  to 
increase  its  power  to  dissolve.  Therefore  if  we  wish 
to  hasten  the  preparation  of  a  solution  or  to  make  a 
stronger  solution  we  heat  the  solvent.  As  has  been 
stated  in  the  first  chapter  some  salts  take  up  heat  when 
they  are  dissolved;  that  is,  the  solution  gets  colder  as 
more  salt  is  dissolved  and  consequently  solution  is 
slow.  This  is  true  of  magnesium  sulphate  (Epsom 
salts),  so  that  when  making  a  solution  of  this  chemical 
it  will  shorten  the  process  materially  if  warm  water 
and  heat  are  used. 

Gases  are  less  soluble  as  the  temperature  is  raised, 
therefore  solutions  of  gases  are  kept  cold.  In  effer- 
vescing magnesium  citrate  the  carbon  dioxide  is  in 
solution  in  the  bottle  on  account  of  the  pressure. 
5 


66  PURIFICATION  OF  SUBSTANCES 

When  the  bottle  is  opened  and  pressure  released  the  gas 
comes  out  of  solution  causing  the  foam.  If  the  citrate 
solution  is  warm  practically  all  the  gas  is  lost,  while 
in  cold  solutions  more  gas  is  retained. 

PURIFICATION  OF  SUBSTANCES. 

Crystallization. — The  difference  in  degree  of  solubility 
is  made  use  of  in  the  separation  and  purification  of 
salts.  An  earth  containing  mixtures  of  salts  is  leached, 
the  solutions  filtered  and  concentrated  to  the  point  of 
crystallization.  When  a  crystal  forms  its  tendency 
is  to  come  out  pure  so  that  by  repeated  crystallization 
salts  may  usually  be  freed  of  their  impurities. 

Water  is  used  extensively  as  the  solvent  in  the 
purification  of  substances,  but  when  the  salts  have 
about  the  same  degree  of  solubility  in  water,  other 
solvents  are  made  use  of. 

Water  itself  can  be  purified  by  successive  crystalliza- 
tion. In  the  changing  of  water  to  its  solid  form  (freez- 
ing), ice  separates  out  purer  than  the  mother  liquor 
each  time.  Many  substances  which  either  crystallize 
with  difficulty  at  very  low  temperatures  or  not  at  all 
are  purified  by  distillation. 

Distillation. — Distillation  is  the  most  widely  used 
and  easiest  method  of  purifying  water1  for  laboratory 

1  One  distillation  is  not  sufficient  to  obtain  absolutely  pure  water. 
The  first  and  last  portions  are  thrown  away  since  they  generally 
contain  soluble  gases  and  ammonia.  Water  distilled  in  glass  con- 
tains a  trace  of  alkali  (lye)  and  that  from  block  tin  stills  contains  a 
trace  of  tin.  Certain  bacteria  grow  in  distilled  water  to  a  slight 
extent  and  even  if  killed  by  heat  they  produce  ill  effects  when  injected 
into  the  body.  Therefore  for  injection  purposes  (salvarsan,  saline, 
etc.),  water  should  be  double  distilled  and  freshly  prepared. 


SUMMARY  OF  CHAPTER  XI  67 

purposes,  etc.  Various  oils  and  alcohol  are  freed  of 
impurities  by  this  method.  In  this  process  the  differ- 
ences in  boiling-point  are  made  use  of:  distillation  is 
allowed  to  proceed  at  a  given  temperature  until  all 
the  vapor  that  comes  off  at  that  temperature  has  been 
recovered  and  the  temperature  is  then  raised  to  obtain 
the  next  fraction.  Such  a  process  is  termed  fractional 
distillation.  Curiously  enough,  mercury  is  separated 
from  substances  with  which  it  occurs  in  nature  by  being 
distilled,  and  the  same  process  is  used  to  further  purify 
this  metal  in  the  laboratory. 

SUMMARY  OF  CHAPTER  XL 

Nearly  all  substances  are  soluble  to  a  greater  or 
less  extent  in  water.  A  large  proportion  of  chemical 
reactions  take  place  in  water  solutions. 

As  a  rule,  heating  increases  the  solvent  power  of 
water  for  liquids  and  solids  and  decreases  its  solvent 
power  for  gases. 

Other  things  being  equal  the  amount  of  gas  dissolved 
in  a  liquid  varies  as  the  pressure  of  that  particular 
gas  on  the  surface. 

The  difference  in  solubilities  of  two  substances  in 
any  given  solvent  make  it  possible  to  separate  the 
substances  by  recrystallization.  Substances  may  be 
freed  of  impurities  by  recrystallization  if  the  im- 
purities possess  a  different  degree  of  solubility. 

Liquids  having  different  boiling-points  may  be 
separated  by  distillation.  Distillation  offers  another 
means  of  purifying  substances. 


CHAPTER  XII. 

NATURAL  WATERS— CHEMICAL  ACTION  OF 
WATER. 

Sea  Water. — Owing  to  its  power  of  dissolving  sub- 
stances, water  as  it  occurs  in  nature  is  almost  always 
impure.  Sea  water  contains  large  amounts  of  salts 
which  the  waters  falling  on  the  surface  of  the  earth 
and  seeping  through  the  crust  have  leached  out  and 
brought  with  them.  The  air  takes  up  the  water  in 
vapor  form  and  leaves  the  salts.  The  Dead  Sea  which 
has  no  outlet  to  the  ocean  contains  a  very  large  quan- 
tity of  salts  (about  25  per  cent.),  so  much  that  the 
specific  gravity  is  very  high  and  it  is  impossible  for  a 
person  to  sink  in  it. 

Lakes,  Rivers,  Springs. — The  amount  of  impurities 
in  the  waters  of  springs,  rivers  and  lakes  depends 
primarily  upon  the  character  of  the  region  through 
which  the  water  flowed.  If  a  spring  is  furnished  by 
waters  flowing  through  sandstones  and  quartz  forma- 
tions it  will  contain  very  little  impurities,  while  springs 
from  salt  deposits  will,  of  course,  contain  varying 
amounts  of  minerals.  Springs  coming  from  very 
deep  sources  where  the  temperature  is  high,  will,  when 
other  things  are  equal,  contain  more  mineral  on 
account  of  the  increase  in  solvent  power  due  to 
increase  in  temperature.  Surface  waters  are  liable  to 
contamination  by  all  sorts  of  impurities  chief  among 
them  are  the  excreta  of  man  and  animals.  Inland 


HARD  AND  SOFT  WATERS  69 

waters  containing  relatively  large  amounts  of  common 
salt  without  other  minerals  in  proportion  are  looked 
upon  by  the  sanitarian  as  possibly  contaminated  by 
man  or  animals.  Other  tests  are  necessary  to  confirm 
this  suspicion. 

Hard  and  Soft  Waters. — Waters  slowly  passing  through 
swamps  take  up  organic  acids  which  increase  the  solv- 
ent action.  Such  waters  passing  over  limestone  will 
take  up  relatively  large  quantities  of  lime  and  become 
what  are  known  as  hard  waters. 

Hard  waters  coagulate  soap  solutions,  that  is,  when 
soap  is  used  in  them  they  become  turbid  and  if  very 
hard  will  precipitate  the  soap  in  flakes  or  curds.  If 
the  hardness  is  due  to  limestone  (calcium  carbonate) 
and  magnesium  carbonate,  boiling  will  drive  off  the 
carbonic  acid  and  allow  the  salts  to  precipitate  and  the 
water  is  soft.  This  is  called  temporary  hardness.  If 
the  water  contains  calcium  sulphate  or  iron  sulphate 
(copperas)  it  is  said  to  be  permanently  hard.  It  is 
plain  that  the  use  of  hard  waters  for  washing  purposes 
is  not  economical  because  so  much  soap  is  needed  to 
produce  any  effect.  The  remedies  generally  used  to 
soften  waters  are:  boiling  or  the  addition  of  borax 
(sodium  biborate). 

Waters  containing  salts  in  any  appreciable  amounts 
should  not  be  used  for  boilers  or  for  steam  sterilizers 
(autoclaves)  because  of  the  residue  they  leave  to  form 
a  cake.  Waters  containing  organic  acids  corrode 
the  sterilizers  and  even  hasten  the  rusting  of  instru- 
ments. A  small  amount  of  sodium  carbonate  (washing 
soda)  is  added  to  the  water  in  which  instruments  are 


70  NATURAL   WATERS 

boiled  in  order  to  neutralize  any  acids  that  may  be 
in  the  water  and  thus  prevent  corroding  and  rusting. 

Rain  Water. — Rain  water  is  soft  and  one  would  think 
it  ought  to  be  pure.  Rain  is  the  cleanser  of  the  at- 
mosphere and  brings  down  besides  the  dust  around 
which  rain  drops  form  certain  gases  like  ammonia. 

Drinking  Water  (Potable  Water).— The  fact  that  a 
water  is  clear  and  cold  and  contains  very  small  amounts 
of  solid  matter  does  not  necessarily  mean  that  it  should 
be  drunk.  One  cannot  judge  the  potability  of  water 
entirely  by  its  taste,  odor,  or  appearance.  Apparently 
the  best  water  may  contain  disease-producing  germs 
like  typhoid,  cholera,  etc.,  so  that  a  water  to  be  safe 
must  conform  to  certain  bacteriological,  as  well  as 
chemical  and  physical  standards.  Fortunately  filtra- 
tion will  also  remove  a  large  percentage  of  the  bacteria. 
Mechanical  filtration,  after  the  addition  of  clarifiers,  is 
often  used,  but  the  safest  filter  is  slow  sand  filtration. 
The  latter  is  a  biological  as  well  as  a  physical  and 
chemical  process.  Each  grain  of  sand  is  coated  with 
a  gelatinous  membrane  due  to  the  growth  of  organisms 
and  the  bacteria  coming  through  impinge  upon  them 
and  are  held.  An  efficient  sand  -filter  removes  97  to 
99  per  cent,  of  the  germs  of  the  water  passing  through 
them. 

Porcelain  filters  through  which  water  is  forced 
under  pressure  are  made  for  home  use  as  well  as  for 
the  laboratory.  Of  this  type  the  Berkefeld  and  the 
Pasteur  are  commonly  used.  They  are  made  in  various 
degrees  of  fineness  and  standardized  according  to  the 
amount  of  water  which  will  pass  through  in  a  given 


SUMMARY  OF  CHAPTER  XII  71 

time  under  a  given  pressure.  No  filter  can  be  said  to 
be  safe  until  it  is  tested  bacteriologically,  and  then 
during  an  epidemic  of  a  water-borne  disease  even  the 
filtered  water  should  be  boiled  before  being  consumed. 

SUMMARY  OF  CHAPTER  XII. 

Natural  waters  are  almost  always  impure.  The 
amount  of  salts  and  other  impurities  in  spring,  river 
or  lake  waters  depends  upon  'the  region  through  which 
the  water  flowed.  Sea  water  and  mineral  springs  con- 
tain large  amounts  of  salts.  Hot  springs  and  deep  well 
waters  are  liable  to  contain  large  amounts  of  salts. 

Water  containing  large  amounts  of  limestone  and 
magnesia  is  said  «to  be  hard.  The  lime  and  magnesia 
form  insoluble  salts  with  soaps  and  no  lather  is  formed 
until  all  the  salts  are  precipitated.  The  use  of  hard 
waters  for  bathing  purposes  is  uneconomical.  Waters 
may  be  softened  by  boiling  or  the  addition  of  borax. 
Waters  containing  calcium  and  magnesium  carbonate 
are  said  to  be  in  a  state  of  temporary  hardness  because 
this  property  can  be  removed  by  boiling.  Permanently 
hard  waters  contain  magnesium,  calcium  or  iron  sul- 
phate. Rain  water  and  distilled  water  are  soft.  Waters 
from  swamps  passing  over  limestone  are  generally 
hard. 

Waters  containing  salts  should  not  be  used  in 
autoclaves  or  boilers  on  account  of  their  scale-forming 
properties. 

The  potability  of  waters  cannot  be  determined 
solely  by  appearance  and  taste.  Polluted  waters  may 
appear  highly  desirable  for  drinking  purposes. 


CHAPTER  XIII. 
COMPOSITION  OF  WATER. 

THE  composition  of  a  substance  is  determined  by 
observations  from  two  stand-points — analysis  and 
synthesis.  By  the  analysis  of  water  accomplished  by 
passing  an  electric  current  through  it  we  find  that 
two  elements  are  obtained.  Hydrogen  is  given  off 
at  one  pole  (negative)  in  twice  the  amount  in  which 
oxygen  is  given  off  at  the  other  (positive)  pole.  This 
shows  us  that  at  least  water  is  composed  of  two  parts 
of  hydrogen  to  one  of  oxygen  or  H2O.  But  there  may 
be  other  substances  liberated  which  do  not  come  off 
as  a  gas,  so  we  test  the  water  remaining  undecomposed 
in  the  flask  but  find  no  other  substances.  Then  we 
make  a  determination  of  the  molecular  weight  of 
water  vapor  by  certain  physical  chemical  means  and 
find  it  to  agree  with  the  formula  H2O.  Now,  if  our 
work  has  been  correct  we  ought  to  be  able  to  synthetize 
water  from  these  two  elements  in  these  proportions. 
So  two  parts  of  pure  hydrogen  gas  and  one  part  of 
pure  oxygen  gas  are  placed  in  a  vessel  and  exploded  by 
means  of  an  electric  spark.  Water  is  formed  and  all 
of  both  gases  disappear.  We  conclude  that  water  is 
composed  of  two  parts  of  hydrogen  to  one  part  of 
oxygen. 

This  reaction  gives  off  a  great  amount  of  heat  and 


ION  I Z  AT  I  ON  73 

the  compound  formed,  water,  is  very  stable.  It  is 
very  difficult  to  decompose  water  by  heat.  In  fact 
water  is  a  very  stable  compound  though  it  may  com- 
bine chemically  with  certain  substances  with  apparent 
ease  it  reacts  as  a  whole  molecule  and  is  not  broken 
up.  It  combines  with  oxides  to  form  the  hydroxides 
such  as  was  indicated  in  the  first  chapter.  Lime  which 
is  the  oxide  of  calcium  (CaO)  is  converted  into  lime 
hydroxide  or  calcium  hydroxide  (Ca(OH)2)  by  water 
thus : 

CaO  +  H2O  =  Ca(OH)2. 

Water  also  combines  with  the  dioxide  (S02)  or 
dioxide  (S03)  of  sulphur  to  form  acids: 

SO2  +  H2O  =  H2SO3  (Sulphurous  acid). 

and 

80s  +  H2O  =  H2SO4  (Sulphuric  acid). 

Water  is  probably  the  most  important  chemical 
compound  known.  It  is  a  by-product  in  great  many 
reactions  in  which  hydrogen  combines  with  an  OH 
group.  For  instance,  in  the  union  of  an  acid  and  a  base 
about  which  we  shall  learn  later,  water  as  well  as  a 
salt  are  formed: 

NaOH         +  HC1  NaCl          +H2O. 

Caustic  soda.  Hydrochloric  acid.  Common  salt. 

In  this  case  the  H  of  the  acid  combined  with  the  OH 
of  the  base.  This  OH  group  is  very  important  in 
chemistry  and  should  be  remembered  for  use  later. 
It  is  called  the  hydroxyl  group. 

lonization. — Substances  in  solution  in  water  do  not 
exist  there  as  closely  bound  elements  but  are  slightly 


74  COMPOSITION  OF  WATER 

pulled  apart;  as:  H — Cl  or  Na — OH.  .The  compound 
is  said  to  be  ionized  or  in  loose  formation  (dissociated). 
Each  component  is  an  ion  and  termed  positive  or 
negative.  The  extent  of  dissociation  depends  upon 
the  dilution,  that  is,  in  weak  solutions,  we  find  more 
dissociation  or  ionization  than  in  strong  solutions. 

When  two  or  moFe  salts  are  in  the  same  solution 
there  is  a  constant  interchange  of  ions.  Suppose, 
for  example,  that  saltpetre  (potassium  nitrate  KNO3) 
is  in  solution  with  common  salt  (sodium  chloride, 
NaCl).  The  former  would  be  dissociated  into  K — NO3 
and  the  latter  into  Na — Cl.  Immediately  there  would 
be  an  interchange  with  the  loose  formation  of  potas- 
sium chloride,  K — Cl  and  of  sodium  nitrate  Na — NO3. 
We  may  imagine  a  sort  of  a  Virginia  reel  formation, 
the  girls  representing  the  negative  ions  and  the  boys 
the  positive  ions.  The  positive  ions  would  swing 
his  partner  then  swing  some  other  negative  ion,  back 
to  his  particular  negative  ion  and  then  to  some  other 
and  so  on  so  long  as  all  combinations  remained  in  the 
game.  Let  us  introduce  another  chemical  like  lunar 
caustic  (silver  nitrate  AgNO3).  When  the  positive 
ion  Ag  is  in  loose  combination  with  any  N03  ion  the 
interchange  proceeds  as  usual  but  when  an  Ag  ion 
comes  in  contact  with  a  Cl  ion  they  form  a  compound 
which  is  insoluble  and  precipitate  from  solution.  In 
terms  of  our  illustration  this  particular  combination  of 
Ag  and  Cl  leave  the  game  immediately  and  this  pre- 
cipitation proceeds  until  either  all  the  Ag  or  the  Cl 
is  used  up.  Either  may  be  in  excess  and  use  up  all  the 
other  and  precipitation  ceases.  This  fact  is  made 


SUMMARY  OF  CHAPTER  XIII  75 

use  of  in  the  determination  of  the  amounts  of  either 
material  in  solution.  If  we  have  a  chloride  in  solution 
and  want  to  know  how  much  chlorine  there  is  present, 
we  add  a  soluble  salt  of  silver  in  excess  and  the  chlorine 
is  precipitated  as  silver  chloride.  This  is  filtered  off, 
washed,  and  weighed.  If  we  have  silver  in  solution- 
some  soluble  chloride  is  added,  and  the  precipitate 
treated  as  above. 

The  question  arises:  How  are  we  to  know  which 
combination  will  be  insoluble  and  will  precipitate? 
The  answer  is:  We  cannot  predict  what  will  happen 
except  by  experience.  We  learn  accidentally  or  by 
trial,  for  example,  that  silver  chloride  is  insoluble  and 
that  a  solution  of  a  soluble  silver  salt  added  to  a 
solution  of  a  chloride  will  form  a  precipitate  and  by 
analysis  we  find  this  precipitate  to  be  silver  chloride. 
In  working  with  chemicals  one  soon  learns  and  easily 
remembers  those  things  which  will  not  remain  in  solu- 
tion together.  These  elements  are  known  in  Materia 
Medica  and  prescription  writing  as  incompatibles. 

Incompatibles. — From  what  we  have  just  learned 
it  is  obvious  that  silver  nitrate  and  sodium  chloride 
cannot  be  put  in  the  same  solution.  Any  salt  of  silver 
is  said  to  be  chemically  incompatible  with  a  chloride. 
The  nurse,  the  pharmacist  and  the  physician  must 
remember  the  incompatible  substances  with  which 
they  have  to  work. 

SUMMARY  OF  CHAPTER  XIII. 

By  analysis  with  an  electric  current  water  is  found 
to  contain  hydrogen  and  oxygen  in  the  ratio  of  two 


76  COMPOSITION  OF  WATER 

volumes  H  to  one  volume  O.  A  mixture  of  2H+1O 
can  be  exploded  by  a  spark.  All  the  gases  disappear 
and  water  is  formed  (synthesis).  Water  therefore  must 
consist  of  H2O  or  some  multiple  of  H20,  as  H4O2,  etc. 
Molecular  weight  determinations  of  steam  give  ap- 
proximately 18,  which  we  find  is  the  sum  of  the  atomic 
weights  of  H2  and  O,  and  not  of  H4  and  O2.  Therefore 
the  formula  of  water  (vapor)  is  H2O. 

Water  is  a  very  stable  compound. 

Water  combines  with  some  oxides  to  form  hydroxides 
(Ca(OH)2,  NaOH,  etc.),  and  with  SO2  or  SO3  to  form 
acids  (H2SO3  =  sulphurous  acid;  or  H2S04  =  sulphuric 
acid). 

An  acid  and  a  base  combine  to  form  a  salt  plus 
water. 

The  group  OH  is  called  hydroxyl. 

Substances  in  solution  are  ionized  or  slightly  dis- 
sociated. There  is  a  constant  and  rapid  interchange 
of  ions  until  two  ions,  which,  when  united  form  an 
insoluble  compound.  These  two  ions  and  similar 
ions  drop  out  of  the  field  of  interaction.  Precipitation 
continues  as  long  as  both  varieties  of  ion  are  present 
(i.  e.y  until  one  kind  is  used  up). 

Any  two  substances  which  cannot  exist  together  in 
the  same  solution  are  said  to  be  incompatible. 


CHAPTER  XIV. 
HYDROGEN  PEROXIDE. 

WATER  is  the  monoxide  of  hydrogen  H2O,  while 
hydrogen  peroxide  is  the  dioxide  H2O2.  It  is  water 
plus  one  atom  of  oxygen. 

Preparation. — Hydrogen  peroxide  does  not  occur  in 
nature  in  any  appreciable  amounts  as  far  as  we 
know.  It  is  perhaps  in  the  atmosphere  in  very  small 
quantities. 

It  is  prepared  by  treating  the  peroxide  of  barium 
BaO2  with  hydrochloric  acid  2HC1. 

Ba02  +  2HC1  =  BaCl2  +  H2O2. 

It  is  then  purified  by  fractional  distillation  (see 
Chapter  X).  The  ordinary  solution  on  the  market  is 
a  3  per  cent,  solution  in  water,  though  a  30  per  cent, 
solution  can  be  purchased. 

Properties. — Pure  hydrogen  peroxide  is  a  clear  color- 
less liquid  very  much  like  water  but  is  one  and  one-half 
times  heavier  (specific  gravity  =  1.4996).  It  has  no 
odor,  possesses  a  peculiar,  slightly  acrid,  taste  and 
produces  a  soapy  froth  when  taken  into  the  mouth. 
It  gives  up  the  extra  atom  of  O  on  standing,  especially 
in  a  warm  place  and  exposed  to  light.  It  should, 
therefore,  be  bottled  in  amber-colored  glass  and  kept 
in  the  ice-box.  The  solutions  of  3  per  cent,  hydrogen 
peroxide  on  the  market  generally  contain  a  small 


78  HYDROGEN  PEROXIDE 

amount  (-5-  grain  to  the  ounce)  of  acetanilid  to  preserve 
it.  Old  solutions  should  not  be  used.  It  is  safer  to 
replace  the  stopper  with  a  cotton  plug,  which  allows 
any  liberated  gas  to  escape. 

Uses. — Hydrogen  peroxide  gives  up  its  oxygen  to 
oxidizable  substances  in  the  sense  of  the  following 
equation: 

H202  =  H20  +  O. 

It  is  therefore  useful  as  an  oxidizing  agent.  The 
30  per  cent,  solution  is  rarely  used  in  medicine;  when 
dropped  on  the  skin  it  is  very  caustic.  The  3  per  cent, 
solution  is  non-poisonous  and  is  an  antiseptic  and  for 
these  reasons  used  in  cleaning  ulcers  and  infected 
wounds.  On  coming  in  contact  with  pus,  blood  or 
living  tissues  it  gives  up  its  oxygen  which  can  act  in 
nascent  form  to  kill  bacteria  and  destroy  pus.  By 
means  of  the  bouyant  effect  of  the  gas  it  is  useful  in 
cleaning  remote  portions  of  a  wound  but  should  never 
be  used  in  a  deep  or  punctured  wound  because  the 
pressure  of  the  gas  liberated  may  drive  the  infection 
further  up  in  the  tissues.  It  is  useful  in  diphtheria  and 
other  throat  infections  and  as  a  mouth  wash. 

Hydrogen  peroxide  is  also  capable  of  bringing  about 
the  reduction  of  compounds  containing  oxygen.  The 
affinity  of  the  atom  of  O  in  H2O2  for  other  atoms  of  O 
is  so  strong  that  it  unites  with  one  atom  to  form  a 
molecule  of  oxygen,  O2. 

Catalyzers. — Substances  like  blood,  and  pus,  etc., 
which  decompose  hydrogen  peroxide  are  said  to  con- 
tain catalases  (ferments),  which  bring  about  the 
liberation  of  the  oxygen  but  do  not  enter  into  the 


SUMMARY  OF  CHAPTER  XIV  79 

products  of  the  reaction.  A  small  amount  of  catalase 
will  decompose  an  unlimited  amount  of  H2O2  and 
remain  active.  Platinum  in  a  finely  divided  condition, 
will  decompose  hydrogen  peroxide,  and  is  an  example 
of  an  inorganic  catalyzer. 

When  zinc  is  acted  upon  by  HC1  with  the  formation 
of  H,  a  small  amount  of  stannous  (tin),  chloride  or 
platinum  chloride  is  put  in  to  accelerate  the  reaction. 
It  helps  the  reaction  proceed  but  is  not  used  up — a 
small  amount  is  useful  indefinitely. 

Another  example  of  a  catalyzer  which  is  made  use 
of  in  ordinary  life  in  platinized  asbestos  as  a  pocket 
lighter.  Methyl  (wood)  alcohol  in  a  metal  vial,  gives 
off  fumes  which  come  into  contact  with  some  platinized 
asbestos.  Air  is  allowed  to  mix  with  it  and  acting 
under  the  influence  of  the  finely  divided  platinum  the 
oxygen  begins  to  combine  with  the  alcohol.  This 
reaction  generates  heat  until  there  is  enough  heat  to 
ignite  its  alcohol  fumes  into  a  blaze. 

SUMMARY  OF  CHAPTER  XIV. 

Hydrogen  peroxide  is  water  plus  one  atom  of  oxygen, 
that  is,  H202. 

It  is  prepared  by  treating  barium  peroxide,  BaO2 
with  HC1  and  distilling. 

Hydrogen  peroxide  is  an  oxidizing  agent,  easily 
giving  up  the  extra  atom  of  oxygen  in  nascent  form. 
It  can  also  act  as  a  reducing  agent  on  compounds  con- 
taining oxygen.  It  possesses  germicidal  power.  The 
ordinary  solution  is  3  per  cent.  Stronger  solutions  are 


80  HYDROGEN  PEROXIDE 

dangerous.  All  solutions  should  be  kept  in  a  dark,  cool 
place  and  preferably  in  a  cotton-plugged  bottle. 

When  hydrogen  peroxide  comes  into  contact  with 
living  tissues  it  is  decomposed  by  certain  ferments 
called  catalyzers.  There  are  also  certain  inorganic 
substances  like  platinum  black,  which  act  catalytically 
on  H2O2. 

In  cleaning  wounds  with  hydrogen  peroxide  solutions 
care  should  be  exercised  in  its  use.  There  is  liability 
of  forcing  the  infecting  agents  more  deeply  into  the 
tissues.  Hydrogen  peroxide  should  not  be  employed 
in  dressing  deep  and  punctured  wounds. 


CHAPTER  XV. 

CHLORINE. 

(At.  wt.  =  34.45.) 

Occurrence. — Chlorine  does  not  occur  in  nature 
free,  but  in  very  large  amounts  in  combination  with 
other  elements.  It  is  one  of  the  chief  elements  in 
sea  water,  being  found  there  combined  with  sodium, 
potassium,  magnesium,  and  others.  It  occurs  also 
throughout  the  crust  of  the  earth  in  soluble  and 
insoluble  combinations.  As  soon  as  water  comes  in 
contact  with  the  soluble  salts  they  are  dissolved  and 
carried  to  the  sea.  About  one-third  of  the  salts  of  the 
Dead  Sea  is  sodium  chloride  (table  or  common  salt), 
that  is,  there  are  seven  pounds  of  sodium  chloride  in 
every  hundred  pounds  of  the  water. 

Animal  bodies  contain  chlorine,  as  chlorides  in 
relatively  large  amounts.  Blood  contains  about  0.8 
parts  sodium  chloride  per  hundred.  It  is  given  off 
in  the  urine,  sweat  and  feces  in  large  amounts.  Well 
waters  contaminated  with  sewage  even  remotely  will 
exhibit  evidences  of  pollution  by  reason  of  high  chlorine 
content. 

Preparation. — The  laboratory  method  of  producing 
chlorine  is  to  heat  manganese  dioxide  with  hydro- 
chloric acid.  The  latter  is  oxidized  to  form  water 
and  sets  free  chlorine: 

MnO2  +  4HC1  =  MnCl2  +  2H2O  +  C12, 


82  CHLORINE 

An  easier  method  is  to  allow  hydrochloric  acid  to 
act  on  bleaching  powder. 

Commercially  chlorine  is  produced  by  passing  an 
electric  current  through  sea-water.  The  sodium  chloride 
is  broken  up  setting  free  chlorine  and  hydrogen,  and 
leaving  behind  soda  lye. 

Uses. — Chlorine  is  a  disinfectant  and  finds  use  as 
such  in  the  cleaning  of  closets,  drains,  etc.,  and  in 
the  disinfection  of  excreta  from  patients  having  in- 
fectious diseases.  It  is  a  very  active  element  when 
free,  attacking  metals  and  bleaching  colors,  and  for 
these  reasons  must  be  used  with  care.  It  is  applied 
in  the  form  of  bleaching  powder  (hypochlorite  of  lime, 
which  see).  In  recent  years  chlorine  has  been  used  in 
the  treatment  of  public  water  supplies  to  rid  them  of 
infectious  organisms.  One  part  of  chlorine  in  5,000,000 
parts  of  water  is  sufficient.  In  this  case  also  it  is 
applied  in  the  form  of  bleaching  powder. 

Chlorine  water  is  found  in  the  U.  S.  Pharmacopoeia 
as  Liquor  Chlori  Compositus,  but  is  very  rarely  used. 

Properties. — Chlorine  is  a  yellowish-green  gas,  soluble 
in  water  with  the  production  of  a  yellow  solution. 
It  has  a  characteristic  odor  and  is  very  irritating  to 
mucous  membranes  when  inhaled.  It  should  be 
handled  with  great  care  and  all  experiments  with  it 
carried  out  under  a  hood  with  good  ventilation.  It  is 
heavier  than  air  and  settles  to  the  bottom  of  the 
hood. 

Chlorine  is  very  active  chemically:  it  combines 
with  almost  all  elements.  Copper,  iron,  phosphorus, 
sodium,  potassium,  etc.,  burn  in  chlorine  gas  just  as 


PREPARATION  83 

in  oxygen.  Most  of  those  mentioned  do  not  have 
to  be  ignited;  for  example,  if  copper  foil  is  placed 
in  chlorine  gas  it  glows  and  CuCl2  is  formed.  Sodium 
and  potassium  unite  with  moist  chlorine  almost  ex- 
plosively forming  the  chlorides.  As  a  general  rule 
chlorides  of  metals  with  the  exceptions  of  silver  and 
lead  are  soluble  in  water. 

Hydrochloric  Acid. — Reference  has  already  been 
made  to  the  fact  that  hydrogen  gas  and  chlorine  gas 
combine  volume  for  volume.  If  equal  volumes  of  these 
gases  in  an  absolutely  dry  state  be  placed  together 
and  an  electric  spark  passed  through,  nothing  wTill 
happen,  but  if  a  minute  trace  of  moisture  be  present 
the  mixture  will  explode,  forming  two  volumes  of 
hydrochloric  acid  gas.  The  formula  for  hydrochloric 
acid  is  HC1,  or  some  multiple  of  this  as  H2C12  or  H3C13, 
etc.,  because  they  combine  in  equal  volumes.  If  now  we 
determine  the  molecular  weight  of  hydrochloric  acid 
we  find  it  equal  to  36.458.  Since  H  =  1.008  and  Cl  = 
35.45,  then  HiCli  must  be  the  formula.  If  our  formula 
were  H2C12  or  more  then  the  molecular  weight  determi- 
nations would  give  higher  figures  as  72.916  or  109.374, 
etc. 

Occurrence  of  HC1. — Hydrochloric  acid  interests  us 
because  it  occurs  free  in  the  stomach.  It  is  secreted 
normally  by  glands  in  the  stomach  wall  and  is  necessary 
in  the  peptic  digestion  of  meats,  eggs,  etc. 

Preparation. — Hydrochloric  acid  is  produced  on  a 
commercial  scale  by  allowing  sulphuric  acid  to  act  on 
a  chloride  like  sodium  chloride  (common  salt).  Sul- 
phuric acid  has  a  stronger  affinity  for  a  base  than 


84  CHLORINE 

hydrochloric  and  therefore  displaces  it  in  the  sense 
of  the  following  equation: 

2NaCl  +  H2SO4  =  Na2SO4  +  2HC1. 
Sodium  Sodium 

chloride.  sulphate. 

We  shall  later  learn  how  sulphuric  acid  is  produced. 

Uses. — Hydrochloric  acid  is  used  extensively  in  the 
industries  and  in  chemical  analysis  and  synthesis.  In 
medicine  it  is  administered  in  dilute  form  to  patients 
who  have  an  insufficient  secretion  of  acid  in  the  stomach. 

Properties. — As  has  been  stated  hydrochloric  acid  is 
a  gas.  We  shall  come  to  know  it  in  water  solution. 
Water  will  absorb  the  gas  until  a  39  per  cent,  solution 
is  formed.  This  is  the  concentrated  Hydrochloric 
Acid  (sometimes  called  Muriatic  Acid)  of  commerce. 
It  has  a  pungent  odor  and  its  fumes  strongly  irritate 
mucous  membranes.  It  burns  the  skin  and  destroys 
clothing. 

The  dilute  hydrochloric  acid  of  the  Pharmacopoeia 
contains  10  per  cent,  of  the  gas  (1  part  of  concentrated 
hydrochloric  acid  plus  3  parts  water). 

Hydrochloric  acid  attacks  metals  such  as  iron  and 
zinc  with  the  liberation  of  hydrogen  and  the  formation 
of  the  chloride  of  the  metal: 

Zn  +  2HC1  =  ZnCl2  +  H2. 

Zinc 
chloride. 

All  the  characteristics  of  an  acid  obtain  in  hydro- 
chloric acid.  It  is  in  order  then  to  discuss  briefly  the 
acids  in  general. 

Acids. — To  say  that  a  substance  is  an  acid  is  to  say 
it  is  sour  (Latin  acidits  =  sour).  Besides  attacking 


TEST  FOR  HYDROCHLORIC  ACID  85 

metals  with  the  formation  of  hydrogen  as  indicated 
above,  acids  unite  with  bases  (like  soda  lye)  to  form 
salts  and  water: 

NaOH  +  HC1      =  NaCl  +  H2O. 
Sodium  Sodium  chloride 

hydroxide.  (common  salt). 

Acids  turn  blue  litmus1  red. 

The  sour  taste  of  an  acid  has  been  found  to  be  due 

to   the   ionized   hydrogen.       In   water   hydrochloric 

+ 
acid  is  dissociated  into  H  —  Cl.     Vinegar  is  an  acid 

(acetic  acid)  and  its  sourness  is  due  likewise  to  the 

+ 
dissociated   H   (acetic  acid  in  water  =  CH3CO2  —  H). 

Acids  then  are  substances  possessing  a  sour  taste; 
chemically  we  say  a  compound  possesses  acid  properties 
which,  when  dissolved  in  some  dissociating  solvent 
(like  water),  yields  hydrogen  ions. 

Test  for  Hydrochloric  Acid.  —  To  detect  hydrochloric 
acid  in  a  solution,  we  place  in  it  a  piece  of  paper  colored 
with  blue  litmus  (litmus  paper),  and  should  it  turn 
red  we  know  that  some  sort  of  an  acid  is  present. 
Having  determined  that  some  acid  (an  ionized  H)  is 
present  we  want  to  see  whether  chlorine  is  the  other  ion. 

We  remember  from  the  paragraph  on  dissociation 
that  when  a  Cl  ion  comes  in  contact  with  a  silver  ion 
a  precipitate  is  formed.  We  therefore  add  some  soluble 
salt  of  silver  and  in  solution  it  is  ionized. 


+  Ag  --  NO3  =  AgCl  +  H  -  NOs. 
Dissociated       Silver 
silver  nitrate,  chloride. 

1  Litmus  is  a  blue  dyestuff  obtained  by  fermenting  certain  coarsely 
ground  lichens.  It  is  used  to  test  for  acids,  turning  red  when  they 
are  present  and  are  turned  back  to  blue  by  bases.  When  acids  are 
completely  and  exactly  neutralized  by  bases,  the  salts  formed  have 
no  effect  on  red  or  blue  litmus. 


86  CHLORINE 

The  AgCl  comes  down  as  a  white  precipitate  which 
turns  dark  on  standing.  It  is  soluble  in  ammonia. 
We  added  silver  nitrate  and  obtained  a  precipitate  of 
silver  chloride,  therefore  there  must  have  been  an  ion- 
ized Cl  present,  and  hydrochloric  acid  was  in  solution. 

Bleaching  Powder. — When  chlorine  is  passed  into 
slaked  lime  (calcium  hydroxide  Ca(OH)2),  calcium 
hypochlorite  and  calcium  chloride  are  formed. 

2Ca(OH)2  +  2C12  =  CaCl2  +  Ca(OCl)2  +  2H2O. 
Calcium         Calcium 
chloride,     hydrochlorite. 

The  mixture  is  put  on  the  market  as  bleaching 
powder,  so  named  on  account  of  its  ability  to  bleach. 
In  slightly  acid  solutions  chlorine  is  liberated.  On 
account  of  the  very  great  chemical  activity  of  chlorine 
colors  are  bleached  and  bacteria  killed.  Reference 
has  already  been  made  (under  chlorine)  to  the  dis- 
infecting power  of  this  substance. 

Other  Compounds  of  Chlorine. — Chlorine  combines 
with  oxygen  and  with  sulphur  to  form  a  large  number 
of  compounds  but  they  are  not  of  interest  here.  The 
chlorides  of  the  metals,  which  are  of  interest  here, 
will  be  discussed  under  the  particular  metals. 

SUMMARY  OF  CHAPTER  XV. 

Chlorine  occurs  extensively  in  nature  in  common 
salt  beds  (sodium  chloride)  and  sea  water  (chlorides  of 
several  metals) .  It  is  a  very  prominent  and  important 
mineral  constituent  of  the  animal  body.  Blood  con- 
tains about  0.8  per  cent.  NaCl. 


SUMMARY  OF  CHAPTER  XV  87 

Chlorine  is  prepared  by  treating  bleaching  powder 
with  hydrochloric  acid  or  oxidizing  HC1  with  MnO2. 
Commercially  it  is  produced  by  passing  an  electric 
current  through  brine. 

Free  chlorine  is  used  as  a  bleaching  and  as  a  steriliz- 
ing agent.  One  part  free  chlorine  in  5,000,000  parts 
of  water  kills  disease-producing  organisms  like  the 
bacillus  of  typhoid  fever. 

Chlorine  is  a  yellowish-green  gas  with  a  characteristic 
odor.  It  is  very  active  chemically.  Metals  like  copper, 
iron,  and  sodium  burn  in  it,  forming  chlorides. 

Hydrogen  unites  with  chlorine  to  form  a  very 
important  compound,  hydrochloric  acid  (HC1). 

Hydrochloric  acid  is  found  normally  in  the  human 
stomach  where  it  is  necessary  for  protein  digestion. 
When  there  is  not  sufficient  acid  in  the  stomach  HC1 
is  administered  by  mouth  in  dilute  form.  The  concen- 
trated hydrochloric  acid  of  commerce  is  a  39  per  cent, 
solution  of  the  gas  in  water.  It  is  prepared  by  treating 
a  chloride  with  concentrated  sulphuric  acid. 

Hydrochloric  acid  attacks  metals  like  zinc,  forming 
the  chloride  of  zinc  (ZnCl2)  and  setting  free  hydrogen 
gas.  (See  Preparation  of  Hydrogen.) 

The  chemical  definition  of  an  acid  is  as  follows: 
an  acid  is  a  compound  of  H  with  some  radical  or  nega- 
tive element  which  when  dissolved  in  water  yields 
hydrogen  ions.  Likewise,  bases  yield  hydroxyl  groups 
(OH)  on  dissociation.  Acids  and  bases  neutralize 
one  another,  producing  salts. 

The  test  for  hydrochloric  acid  (or  a  chloride)  is  the 
addition  of  some  soluble  silver  salt.  If  chlorides  are 


88  CHLORINE 

present  a  white  precipitate  of  AgCl  appears.  This 
precipitate  can  be  dissolved  by  adding  a  small  amount 
of  ammonia. 

Bleaching  powder  is  formed  by  passing  chlorine 
gas  over  water-slaked  lime.  The  mixture  of  calcium 
chloride  and  calcium  hypochlorite  formed  constitute 
bleaching  powder. 


CHAPTER  XVI. 
BROMINE— IODINE— FLUORINE. 

BROMINE  (At.  wt.  =  80). 

Occurrence. — Bromine,  like  chlorine,  never  occurs  free 
in  nature.  It  is  found  combined  with  metals  forming 
the  bromides  in  salt  deposits  and  in  the  sea,  though 
not  in  such  quantities  as  the  chlorides  are  found. 

Preparation. — The  bromine  salts  may  be  decomposed 
by  an  electric  current  to  produce  bromine,  or  sulphuric 
acid  may  be  used  to  set  free  hydrobromic  acid  (just 
as  hydrochloric  acid  is  produced)  thus: 

2NaBr  +  H2SO4  =  Na2SO4  +  2HBr. 

and  we  may  free  the  bromine  of  the  hydrobromic  acid 
from  its  H  by  allowing  the  H  to  combine  with  O 
through  the  agency  of  some  oxidizing  agents: 

2HBr  +  MnO2  +  H2SO4  =  MnSO4  +  2H2O  +  Br2. 

Uses. — Bromine  itself  finds  very  little  use  in  medicine. 
It  is  used  in  the  laboratory  in  one  of  the  methods  of 
urine  analysis  and  is  useful  in  synthetic  chemistry. 
The  salts,  especially  sodium,  potassium,  lithium,  and 
strontium  as  nerve  depressants. 

Properties. — Bromine  is  a  very  heavy,  dark,  brownish- 
red,  mobile  liquid,  evolving  at  ordinary  temperatures 
reddish  fumes,  highly  irritating  to  the  eyes  and  mucous 


90  IODINE 

membranes.     Its    odor   is    peculiar    and    penetrating, 
resembling  chlorine. 

Its  chemical  properties  are  very  much  like  chlorine: 
in  combination  with  the  metals  bromides  are  formed 
and  in  union  with  hydrogen  hydrobromic  acid  results. 
The  silver  salt  (AgBr)  silver  bromide  is  insoluble  in 
water  like  silver  chloride,  so  that  the  addition  of  a 
soluble  silver  salt  is  also  a  test  for  bromides.  The 
appearance  of  the  precipitate  obtained  (AgBr)  is 
indistinguishable  by  inspection  from  the  precipitate 
obtained  with  chlorides.  Chemically  we  are  able 
to  detect  the  difference  by  adding  a  few  drops  of 
ammonia  to  the  precipitate:  if  the  precipitate  is 
dissolved  quickly  we  know  it  is  silver  chloride — if  it 
is  dissolved  with  difficulty  it  is  silver  bromide. 

IODINE  (At.  wt.  =  127). 

Occurrence. — Iodine  is  very  widely  distributed  in 
nature  but  occurs  in  small  quantities.  It  is  found  in 
small  amounts  with  the  chlorides  and  bromides  in 
deposits  and  in  the  sea.  It  was  first  found  in  sea  weed 
ash  and  has  since  been  detected  in  other  plants  and 
in  the  lower  and  higher  forms  of  animal  life  found  in 
the  sea.  It  is  stated  that  a  certain  tropical  sponge 
contains  14  per  cent,  (of  the  dry  matter)  iodine.  In 
mammals  it  seems  to  play  a  very  important  role  in  the 
thyroid1  gland  since  it  is  found  there  in  considerable 
amount.  (In  the  sheep  over  9  per  cent,  of  the  dried 

1  The  thyroid  gland  is  found  in  the  front  of  the  neck.  It  is  an 
enlargement  of  this  gland  that  is  called  goitre. 


USES  91 

gland  is  iodine.)  White  blood  corpuscles  also  contain 
a  very  small  amount  of  iodine  in  their  composition. 

Iodine  is  also  found  in  minute  quantities  in  the  air 
and  dust. 

Preparation. — Most  of  the  iodine  is  extracted  as  a 
sodium  salt  (sodium  iodate,  NaIO3)  from  the  salt- 
petre deposits  of  Chile.  Europe  and  Japan  furnish 
perhaps  a  third  of  the  world's  production  (750  tons 
per  year).  The  iodate  is  freed  of  its  oxygen  by  means 
of  a  reducing  agent,  such  as  sulphurous  acid  and 
the  iodine  set  free  by  means  of  the  sulphuric  acid 
formed : 

(1)  2NaIO3  +  6H2SO3  =  2NaI  +  6H2SO4. 

(2)  2NaI  +  2H2SO4  =  Na2SO4  +  2HI. 

(3)  2HI  +  H2SO4  =  H2SO3  +  H2O  +  I2. 

These  reactions  take  place  in  the  same  operation,  and 
it  will  be  seen  that  1  molecule  of  H2SO3  is  reformed, 
therefore  in  carrying  out  such  a  process  only  5  parts 
H2SO3  are  needed  instead  of  6  parts  as  indicated  in 
equation  1. 

Uses.— Iodine  was  discovered  a  hundred  years  ago, 
but  was  not  employed  in  medicine  until  1831.  Today 
it  is  used  more  widely  in  medicine  and  surgery  than 
any  other  substance.  It  is  a  counter-irritant,  parasiti- 
cide, absorbent,  and  alterative.  It  is  widely  used  to 
disinfect  wounds  and  is  finding  application  more  and 
more  for  preparing  the  site  of  operation  and  the 
operator's  hands.  It  is  more  efficient  when  the  tissues 
are  dry. 

Iodine  is  used  in  chemical  synthesis  and  analysis, 
and  in  staining  in  the  bacteriological  laboratories. 


92  IODINE 

In  combination  with  hydrogen  as  hydriodic  acid 
(HI)  and  as  the  iodides  of  sodium,  potassium,  and 
lithium,  it  is  employed  extensively  in  treatment.  The 
world's  consumption  is  about  750  tons  per  year. 

Properties. — Iodine  is  a  heavy  blue-black  solid,  with 
a  metallic  luster.  When  heated  these  crystalline  scales 
do  not  melt  but  vaporize  immediately,  giving  off  dark 
purple  fumes.  The  vapor  will  deposit  in  needle  crystals 
on  coming  into  contact  with  a  cool  surface;  in  fact 
these  properties  are  made  use  of  in  the  purification 
of  iodine.  The  process  is  called  sublimation. 

Iodine  is  soluble  in  alcohol  and  chloroform  but  very 
slightly  soluble  in  water.  When  potassium  iodide  is 
present  it  will  go  into  water  solution  easily,  producing 
what  is  known  in  the  laboratory  as  Lugol's  solution. 

Chemically,  iodine  is  an  oxidizing  agent  like  chlorine 
and  bromine;  that  is,  in  water  solution  it  unites 
with  the  H  of  the  water  in  the  presence  of  a  reducing 
agent  and  leaves  the  O  of  the  water  free  to  combine 
with  this  reducing  agent.  Thus  sulphur  dioxide  (SO2), 
a  reducing  agent,  is  oxidized  to  sulphur  trioxide  (SO3) 
by  iodine  in  the  presence  of  water. 

Silver  iodide  is  insoluble  in  water  and  ammonia. 
It  differs  from  the  chloride  and  iodide  in  color;  silver 
iodide  is  yellow  while  the  other  two  silver  salts  are  white. 

Silver  iodide  is  darkened  on  exposure  to  light  though 
not  as  much  as  silver  bromide.  This  change  affected 
by  light  is  the  basis  of  photography,  which  will  be 
discussed  in  the  chapter  on  Silver  and  its  Salts. 

Iodine  possesses  the  peculiar  characteristic  of  com- 
bining with  starch  to  produce  a  blue  color  which  dis- 


SUMMARY  OF  CHAPTER  XVI  93 

appears  on  boiling  and  returns  on  cooling.  Iodine 
will  produce  the  blue  color  only  when  it  is  uncombined ; 
thus  hydriodic  acid  or  potassium  iodide,  etc.,  will 
not  blue  a  solution  of  starch.  This  reaction  may 
be  used  to  test  for  either  starch  or  iodine — if  iodine 
is  sought  in  a  solution  add  starch  solution — if  starch 
be  sought  add  a  drop  or  two  of  Lugol's  solution. 

FLUORINE  (At.  wt.  =  19). 

Fluorine  is  an  active  element  belonging  to  the  same 
group  as  chlorine,  bromine,  and  iodine.  It  never  occurs 
uncombined  in  nature.  It  is  found  as  fluor  spar 
(calcium  fluoride)  which  is  used  as  a  flux  in  iron 
furnaces. 

Fluorine  is  prepared  in  a  manner  similar  to  the 
method  used  for  chlorine,  and  on  account  of  its  activity 
cannot  be  kept  in  glass  but  is  bottled  in  paraffin.  Its 
chief  interest  to  us  lies  in  the  fact  that  the  sodium  salt 
is  sometimes  used  unlawfully  as  a  preservative  in  foods. 

Hydrofluoric  acid,  HF,  is  used  to  etch  glass. 

The  Halogens. — These  four  elements,  chlorine, 
bromine,  iodine,  and  fluorine  form  a  group  known  as 
the  halogens  (salt-producing).  They  possess  certain 
chemical  and  physical  similarities  of  especial  interest 
to  the  chemist,  but  have  no  application  here. 

SUMMARY  OF  CHAPTER  XVI. 

Bromine  is  a  very  heavy,  dark,  brownish-red,  mobile, 
caustic  liquid.  It  never  occurs  free  in  nature.  It 
is  found  as  a  salt  (e.  g.,  NaBr)  in  the  sea. 


94  FLUORINE 

It  is  produced  by  passing  an  electric  current  through 
a  solution  of  a  bromide. 

Bromine  is  little  used  in  medicine  but  is  employed 
extensively  in  synthetic  chemistry.  In  its  chemical 
properties  bromine  is  very  similar  to  chlorine. 

Iodine  is  a  heavy,  blue-black  solid  with  a  metallic 
luster.  It  does  not  melt  but  vaporizes  and  can  be 
sublimed.  It  is  soluble  in  alcohol  and  chloroform. 
Very  slightly  soluble  in  water,  though  it  will  dissolve 
in  a  solution  of  KI  in  water  (Lugol's  solution). 

Iodine  is  found  as  sodium  and  potassium  iodate 
in  Chile  saltpetre  deposits  and  in  sea  weeds.  It 
is  prepared  by  treating  the  iodate  with  sulphurous 
acid. 

Iodine  is  perhaps  the  most  widely  used  substance 
employed  in  medicine  and  surgery.  It  is  employed 
as  counter-irritant,  parasiticide,  absorbent,  and  altera- 
tive. Its  chemical  properties  are  similar  to  those 
possessed  by  chlorine  and  bromine  though  it  is  not  so 
active  chemically.  Starch  solutions  turn  blue  in  the 
presence  of  free  iodine  in  cold  solutions,  on  account 
of  the  formation  of  starch — iodide. 

Fluorine  is  the  most  active  of  this  group  of  halogens 
and  must  be  kept  in  paraffin.  On  account  of  its  power 
to  attack  glass  HF  is  used  in  etching  and  forms  the  basis 
of  diamond  inks.  The  sodium  salt  is  sometimes  used 
illegally  as  a  food  preservative. 

Chlorine,  bromine,  iodine  and  fluorine  belong  to  a 
group  known  as  the  halogens  (salt-producing). 


CHAPTER  XVIT. 

SULPHUR. 

(At.  wt.  =  32.) 

Occurrence. — Sulphur  is  found  in  a  free  state  as 
brimstone  in  volcanic  areas1  and  in  combination  in 
mineral  deposits.  Fool's  gold  which  one  sometimes 
sees  in  coal  is  a  combination  of  sulphur  and  iron, 
Fe2S3  (iron  sulphide).  Sulphides  of  copper,  zinc,  lead, 
etc.,  also  occur  in  large  quantities  in  the  earth's  crust. 
The  so-called  sulphur  springs  contain  hydrogen  sul- 
phide, H2S,  in  solution. 

On  exposure  to  oxygen  and  oxidizing  agents  hydrogen 
sulphide  deposits  sulphur: 

2H2S  +  O2  =  2H2O  +  2S. 

Sulphur  is  purified  by  distillation.  The  chemically 
pure  product  is  obtained  by  recrystallization  from 
solution  in  carbon  bisulphide. 

Uses. — Sulphur  itself  is  used  in  various  skin  diseases 
due  to  parasites  and  other  causes.  It  is  sometimes 
administered  internally  for  its  cathartic  action,  due, 
doubtless,  to  the  sulphides  formed  in  the  intestinal 
tract,  for  sulphur  itself  is  inert.  Sulphur  is  used  in 
gun  powder,  and  in  the  manufacture  of  certain  kinds 
of  matches. 

1  Sulphur  deposits  are  found  in  Louisiana  in  sufficient  quantities 
to  warrant  mining. 


96  SULPHUR 

Burning  sulphur  is  used  in  fumigations  where  it  is 
desired  to  kill  insects  or  animals,  such  as  rats.  Sulphur 
dioxide  gas  results  from  the  burning  and  this,  while 
not  bactericidal,  is  very  efficient  for  ridding  buildings 
and  vessels  of  insects,  etc.  Sulphites  and  sulphuric 
acid  are  useful  in  many  industries. 

Properties. — Sulphur  is  a  pale  yellow  solid,  light  in 
weight,  melts  at  a  little  above  boiling-point  of  water 
(at  118°  C.)  and  boils  at  about  450°  C.  On  being 
melted  it  becomes  darker  in  color,  gradually  assuming 
a  dark  brown  shade.  The  solid  is  crystalline  or  non- 
crystalline  (amorphous).  It  is  possible  to  obtain 
easily  two  different  kinds  of  crystallized  sulphur. 
Not  only  are  the  shapes  of  these  two  kinds  of  crystals 
different,  but  they  are  found  to  contain  different 
amounts  of  energy. 

Chemical  Properties. — Sulphur  is  relatively  inert  at 
ordinary  temperatures  but  on  heating  will  combine 
with  a  large  number  of  elements.  It  combines  with 
hydrogen  to  form  two  compounds  H2S  and  H2S2. 
The  former  is  far  more  important  as  it  finds  extensive 
use  in  the  laboratory.  By  the  use  of  hydrogen  sulphide 
the  various  metals  can  be  separated  into  groups 
on  account  of  the  differences  in  solubility  of 
their  sulphides.  Every  laboratory  has  a  hydro- 
gen sulphide  generator.  The  odor  of  this  gas  is 
extremely  disagreeable  and  in  large  quantities  poison- 
ous. At  least  a  part  of  the  odor  of  decomposing  flesh 
is  due  to  hydrogen  sulphide. 

Sulphur  combines  with  oxygen  to  form  a  number  of 
compounds,  only  two  of  which  need  be  mentioned. 


VALENCE  97 

SO2,  sulphur  dioxide,  combines  with  water  to  form 

sulphurous  acid: 

so2  +  H2o  =  H2so3, 

which  acid  combines  with  bases  to  form  sulphites. 
The  gas  SO2  is  liquefied  and  put  up  in  cylinders  for 
disinfection  purposes. 

SO2  can  be  oxidized  to  sulphur  trioxide  S03,  a  liquid, 
which  in  the  presence  of  water  becomes  H2SO4, 
sulphuric  acid.  H2SO4  is  used  in  the  preparation  of 
many  compounds  and  as  a  dehydrating  agent.  It  is 
used  in  storage  batteries  and  in  steel  pickling  processes. 

Valence. — The  student  has  doubtless  wondered 
that  two  or  more  compounds  of  the  same  elements 
can  exist  and  also  that  some  compounds  can  hold 
more  hydrogen  in  combination  than  others. 

It  was  seen  that  chlorine  held  one  hydrogen  in 
chemical  union  (HC1)  while  oxygen  held  two  (H2O). 
Bromine,  iodine  and  fluorine  held  one  only,  but  sulphur 
held  two  (H2S).  Later  it  will  be  seen  that  phosphorus 
can  hold  three  or  five.  Now  we  learn  that  sulphur 
can  hold  two  atoms  of  oxygen  or  three  atoms,  and  since 
1O  is  equivalent  to  2H  we  have  sulphur  capable  of 
holding  an  equivalent  of  2H,  of  4H  or  of  6H.  This 
property  of  holding  an  element  in  combination  is  called 
valence.  We  accept  hydrogen  as  the  standard  1 — 
then  since  chlorine  can  hold  one  H,  the  valence  of 
chlorine  is  also  1;  likewise  the  valence  of  O  =  2.1 

1  These  valences  have  been  found  experimentally  and  we  simply 
remember  them  after  we  become  accustomed  to  dealing  with  chemical 
substances.  The  student  who  wishes  to  know  more  of  chemistry 
will  find  a  discussion  of  the  Periodic  Law  of  Mendele'eff  (in  any 
thorough  treatise  on  Chemistry)  very  interesting.  We  are  able  to 
predict  what  the  valence  will  be  in  some  cases  before  an  element  is 
discovered. 
7 


98  SULPHUR 

Some  elements  instead  of  having  a  non- variable 
valence  may  be  able  to  hold  different  hydrogen  equiva- 
lents according  to  the  conditions.  Chlorine  usually 
has  a  valence  of  1,  but  sometimes  it  may  be  3  or  5, 
while  sulphur  is  2,  4,  6  or  even  8. 

The  question  of  valence  is  very  important  in  the 
study  of  the  carbon  compounds,  so-called  organic 
chemistry  to  be  discussed  presently. 

SUMMARY  OF  CHAPTER  XVII. 

Sulphur  is  a  pale  yellow  solid,  melting  at  118°  C. 
and  vaporizing  at  450°  C.  It  may  be  amorphous 
(non-crystalline)  or  crystallize  in  two  forms. 

It  is  found  free  in  nature  in  volcanic  deposits,  and 
purified  by  distillation  or  crystallization  out  of  carbon 
bisulphide. 

Sulphur  is  not  very  active  chemically.  It  can  be 
burned  to  the  dioxide,  SO2,  or  trioxide  S03.  These 
compounds  are  soluble  in  water,  forming  respectively, 
sulphurous  (H2SO3)  and  sulphuric  (H^SCX)  acids. 

Sulphur  unites  with  hydrogen  and  metals  to  form 
sulphides  like  H2S;  Na2S,  etc.  It  is  applied  in  skin 
diseases  and  burned  to  rid  ships,  houses,  etc.,  of  insects 
and  rats.  Burning  sulphur  is  not  advisable  for  fumiga- 
tion after  contagious  diseases,  as  SO2  has  little  germi- 
cidal  action. 

The  power  to  hold  atoms  in  chemical  combination 
is  spoken  of  as  valence.  The  valence  of  H  =  1;  of 
Cl,  Na,  K,  Br,  I,  etc.  =  1,  while  the  valence  of  O,  S, 
Mg,  Pb,  etc.  =2.  An  element  may  possess  different 


SUMMARY  OF  CHAPTER  XVII  99 

valences  as  S,  the  valence  of  sulphur  may  be  2,  4,  6, 
etc.,  of  Hg  may  be  1  or  2  (HgCl  or  HgCl2).  There  is 
no  rule  about  valence  except  the  place  of  the  element 
in  the  periodic  system  and  this  is  complicated.  We 
must  simply  remember  the  valences  of  the  elements 
commonly  dealt  with. 


CHAPTER  XVIII. 

SODIUM,  Na. 
(At.  wt.  =  23.) 

IN  daily  life  and  in  the  hospital  we  come  Into  contact 
more  often  with  compounds  of  this  element  than  any 
other.  Sodium  is  the  metal  of  which  common  salt  is 
the  chloride  and  it  is  the  basic  element  in  soda  lye  and 
washing  and  in  cooking  soda. 

Occurrence. — Sodium,  on  account  of  its  chemical 
activity  is  never  found  free  in  nature.  In  combination 
with  other  elements  it  is  found  everywhere.  The  sea 
contains  large  amounts  of  the  chloride;  great  mines 
of  the  chloride  are  found  in  Germany  and  as  nitrate 
it  forms  the  well  known  Chili  saltpetre  beds.  Dust 
contains  it  in  detectable  amounts  and  even  the  dust- 
free  atmosphere  of  the  midocean  holds  it  in  small 
quantities. 

Sodium  chloride  occurs  in  all  the  tissues  of  the  body 
and  in  the  blood;  there  are  about  eight  parts  in  every 
thousand. 

In  biblical  times  sodium  chloride  was  mined  from 
deposits  containing  other  salts.  The  expression 
"Salt  has  lost  its  savor"  refers  to  lumps  from  which 
all  the  sodium  chloride  was  taken  away  and  some  other 
salt  left.  It  is  impossible  for  pure  sodium  chloride  to 
lose  its  savor  unless  changed  chemically. 


PROPERTIES  ,101 


Preparation — The  chloride  and  '  nitrate  ,  found,  in; 
nature  may  be  purified  by  •  cry^taUi^yo^v  'and  'trie' 
element  itself  is  obtained  by  passing  strong  electric 
currents  through  molten  soda  lye  (NaOH). 

Uses. — The  saline  solution  of  the  hospital  is  a 
solution  of  sodium  chloride.  It  is  an  essential  com- 
ponent of  media  for  growing  microorganisms.  There 
are  over  twenty-five  salts  of  sodium  used  in  medicine. 

As  lye,  extensive  use  is  made  of  sodium  in  various 
industries.  It  is  being  used  more  and  more  in  dye 
and  other  chemical  syntheses. 

Soap  is  sodium  combined  with  acids  from  fats 
as  we  shall  see  when  we  study  fats.  Soda  is 
necessary  in  glass  manufacture — the  silicate  of  sodium 
is  one  of  the  chief  constituents  of  this  useful  substance. 

Properties. — For  a  long  time  soda  lye  was  thought 
to  be  an  element,  but  when  Sir  Humphry  Davy  passed 
an  electric  current  through  it  a  bright  metallic  sub- 
stance rose  to  the  top  and  took  fire  when  it  came  in 
contact  with  air.  This  was  metallic  sodium,  a  soft, 
steel-gray  solid,  which  rapidly  turns  dark  in  air  if 
a  trace  of  moisture  is  present.  Sodium  is  so  active 
that  it  reacts  with  explosive  violence  if  water  is 
poured  on  it.  Sodium  hydroxide  is  formed  and 
hydrogen  is  given  off: 

2Na  +  2H2O  =  2NaOH  +  H2. 

The  heat  generated  by  the  reaction  may  be  sufficient 
to  ignite  the  hydrogen. 

Sodium  combines  with  chlorine  in  the  presence  of 
moisture  to  form  sodium  chloride  (common  salt). 


102  SODIUM 


Jt>is  obtained  from  sea-water  by  evaporation  or  mined 
from  the  salt 'deposits  and  purified  by  recrystallization. 
It  crystallizes  in  characteristic  hopper-shaped  cubes 
which  are  hollow  in  the  centre.  These  crystals  melt 
at  780°,  and  fly  to  pieces  (decrepitate)  when  heated. 
It  is  soluble  in  water  to  the  extent  of  36  parts  per  100; 
i.  e.,  100  parts  saturated  solution  of  sodium  chloride 
contains  36  parts  of  the  salt.  Heat  increases  the 
solubility  very  little. 

Sodium  chloride  is  necessary  for  bodily  function, 
and  therefore  a  necessary  constituent  of  the  food. 
In  flesh  food  it  is  present  in  sufficient  quantities  to 
balance  the  potassium,  calcium,  and  magnesium  salts, 
therefore  carnivorous  animals  do  not  require  salt. 
On  the  other  hand,  plants  contain  more  potassium 
than  sodium,  and  herbivorous  animals  seek  salt  licks 
in  order  to  maintain  the -balance.  Man  subsisting  on 
a  mixed  diet  requires  salt.  To  much  salty  food  without 
organic  acids  (vinegar,  fruit  juices)  has  the  tendency  to 
cause  scurvy. 

Sodium  chloride  is  the  starting-point  in  the  manu- 
facture of  sodium  salts.  If  ammonia  (NH3)  is  added 
to  a  saturated  solution  of  sodium  chloride  and  carbon 
dioxide  (COz)  passed  through  it  at  first  ammonium 
carbonate  is  formed: 


NH3  +  H2O  =  NH4OH. 

Ammonium 
hydroxide. 

NH4OH  +  C02  =  (NH4)HC08. 

Ammonium 
acid  carbonate. 


COOKING  SODA  103 

Now  in  the  presence  of  NaCl  there  is  a  travel  of 
ions,  so  we  have  a  formation  of  ammonium  chloride 
(NH4C1)  and  of  sodium  acid  carbonate,  and  since 
sodium  acid  carbonate  is  insoluble  in  the  already 
saturated  solution  of  salts  it  is  precipitated: 

(NH4)HCO3  +  NaCl  =  NH4C1  +  NaHCOs. 

The  sodium  acid  carbonate  is  filtered  off  and  purified 
by  recrystallization. 

Cooking  Soda. — The  sodium  acid  carbonate  just 
described  above  is  what  we  know  as  cooking  soda. 
When  an  acid  is  added  to  it  carbon  dioxide  gas  is 
given  off: 

NaHCOs  +  HC1  =  NaCl  +  H2O  +  CO2. 

This  is  the  principle  of  the  raising  of  dough — the 
gas  given  off  expands  and  makes  the  bread  light.  In 
practice  hydrochloric  acid  is  not  used  because:  (1) 
the  reaction  would  take  place  before  the  bread  is  heated 
and  all  the  gas  would  come  out  of  the  dough  leaving 
it  flat;  (2)  the  strong  acid  would  affect  the  other 
ingredients;  and  (3)  the  resulting  compound,  NaCl, 
would  make  the  bread  too  salty.  For  these  reasons 
a  weak  acid  is  used  so  that  the  reaction  does  not  take 
place  until  the  dough  becomes  thick  enough  to  hold 
the  gas.  An  organic  acid  like  lactic  (the  acid  found 
in  sour  milk)  or  tartaric  (manufactured  from  grapes) 
is  used.  The  latter  is  mixed  in  powdered  form  with 
the  sodium  acid  carbonate  and  sold  as  baking  powder. 
On  heating  in  the  presence  of  moisture  the  tartaric 
acid  combines  with  the  sodium  acid  carbonate  to  form 


104  SODIUM 

sodium  tartrate  (Rochelle  salt)  and  C02  is  given  off.1 
Sodium  acid  carbonate  is  called  sodium  bicarbonate, 
for  when  it  is  heated  to  a  high  degree  it  gives  off  one 
part  of  CO2  and  sodium  carbonate  Na2CO3  remains: 

2NaHCO3  =  Na2CO3  +  H2O  +  CO2. 

This  carbonate  is  known  as  washing  soda.  It  has 
more  basic  properties  than  the  bicarbonate.  This 
salt  crystallizes  easily  and  depending  upon  conditions 
combines  with  one,  seven  or  ten  parts  of  water;  that 
is,  we  obtain  the  compounds  Na2CO3.H20;  Na2CO3.- 
7H2O  and  Na2CO3.10H2O.  These  molecules  of  water 
are  not  simply  occluded  within  the  crystal  but  are 
chemically  a  part  of  it  though  it  can  be  driven  off  by 
heat  just  as  the  C02  is  driven  off  from  the  molecule  of 
the  bicarbonate.2  Sodium  carbonate  can  be  obtained 
also  by  leaching  the  ashes  of  sea  weeds. 

Sodium  Hydroxide. — If  sodium  carbonate  is  treated 
with  lime  water  Ca(OH)2,  the  interchange  of  ions 
would  produce  the  following  compounds: 

Na2 CO3. 

Ca (OH)  2. 

Na2 (OH)  2. 

Ca CO3. 

Now,  Ca — CO3  is  an  insoluble  compound,  so  that  it 
is  immediately  precipitated  and  becomes  CaCO3. 
Na2(OH)2  is  soluble  and  resolves  into  the  normal 

1  This  same  reaction  takes  place  when  Seidlitz  powder  solutions 
are  poured  together,  but  here  the  substances  being  in  solution  the 
reaction  takes  place  more  vigorously. 

2  These  molecules  of  water  are  known  as  water  of  crystallization. 
This  same  phenomenon  is  observed  in  many  other  compounds. 


SUMMARY  OF  CHAPTER  XV I H  105 

compound  Na — OH.    The  whole  reaction  is  expressed 
by  the  following  equation: 

Na2CO3  +  Ca(OH)2  =  2NaOH  +  CaCOs. 

The  mother  liquor  after  filtration  is  evaporated  and 
the  soda  lye  (caustic  soda  or  sodium  hydroxide, 
NaOH)  is  left  in  white,  crystalline  lumps.  From 
sodium  hydroxide  the  various  salts  of  sodium  are  easily 
made. 

SUMMARY  OF  CHAPTER  XVIII. 

Sodium  is  a  soft,  steel-gray  solid  which  rapidly  tar- 
nishes in  air  containing  even  a  trace  of  moisture.  A 
small  amount  placed  on  water  reacts  violently  to  form 
sodium  hydroxide  (caustic  soda)  and  sets  free  hydrogen. 
The  hydrogen  soon  catches  fire  on  account  of  the  heat 
of  the  reaction. 

Hydrochloric  acid  added  to  sodium  hydroxide  forms 
sodium  chloride  (common  table  salt),  plus  water. 
Sodium  is  found  everywhere.  Even  dust  contains 
detectable  amounts  of  this  element.  Sodium  chloride 
and  nitrate  occur  in  large  salt  beds  and  the  former 
is  the  principle  salt  of  sea-water.  Sodium  chloride  is 
essential  to  the  animal  organism. 

Cooking  soda  is  sodium  bicarbonate.  Washing  soda 
is  more  strongly  alkaline  and  is  the  normal  carbonate. 
Baking  powder  is  a  mixture  of  sodium  bicarbonate 
plus  some  organic  acid.  When  heated  these  two  sub- 
stances combine  to  form  a  salt  and  liberate  CO2  which 
"raises"  the  dough. 

Sodium  salts  are  characterized  by  their  easy  solu- 
bility in  water.  A  very  minute  portion  of  sodium  or 
a  sodium  salt  imparts  an  intense  yellow  color  to  a  flame. 


CHAPTER  XIX. 
ACIDS  AND  BASES— POTASSIUM. 

WE  have  learned  that  an  acid  is  a  sour  tasting  sub- 
stance which  dissociates  in  solution  into  H  ions  and 
some  other  ions.  An  example  of  this  is  hydrochloric 
acid  which  gives  rise  to  free  H  ions  and  free  Cl  ions  thus : 

+ 

HCl  =  H Cl. 

We  come  to  learn  now  that  a  base  is  a  substance 
which  in  solution  is  dissociated,  giving  rise  to  free 
hydroxyl  (OH)  ions,  as  sodium  hydroxide  Na — OH. 

When  both  an  acid  and  a  base  are  in  the  same  solu- 
tion they  neutralize  one  another 

+    -      +      -       +      - 

H— Cl  +  Na— OH  =  Na— Cl  +  H.OH. 

As  long  as  the  acid  and  base  are  present  in  such 
amounts  that  there  are  as  many  H  ions  as  there  are 
OH  ions  they  exactly  neutralize  one  another  and  the 
solution  is  neutral. 

Molecular  Solutions. — How  do  we  prepare  solutions 
containing  equal  numbers  of  H  and  OH  ions? 

Let  us  take  as  a  standard  1  gram  of  H  in  a  liter  of 
water.  But  the  H  is  bound  up  with  chlorine  if  we  use 
hydrochloric  acid.  Therefore  we  use  such  an  amount 
of  hydrochloric  acid  as  contains  exactly  1  gram  H. 


MOLECULAR  SOLUTIONS  107 

The  atomic  weight  of  H  =  l,  and  of  chlorine  35.45, 
making  the  molecular  weight  of  HC1  =  36.458.  There- 
fore, in  36.45  grams  HC1  there  is  contained  1  gram 
H.  Then  36.45  grams  HC1  in  1  liter  is  our  standard 
solution  which  we  shall  term  a  normal  solution. 

To  prepare  a  solution  of  a  base  to  exactly  neutralize 
our  normal  acid  solution  we  must  have  enough  OH 
ions  in  solution  to  be  equivalent  to  1  gram  H  in  a  liter. 
At.  wt.  of  O  =  16  and  of  H  =  l,  then  mol.  wt.  of  OH 
ion  =  17,  and  we  must  have,  therefore,  17  grams  OH 
to  be  equivalent  to  1  gram  H.  The  at.  wt.  of  Na  = 
23,  OH  =  17,  mol.  wt.  NaOH  =  40.  Therefore, 
in  every  40  grams  NaOH  we  have  17  grams  OH  or 
sufficient  amount  to  neutralize  1  gram  H  ions.  To 
make  a  normal  solution  of  the  base  NaOH  then  we  dis- 
solve 40  grams  NaOH  in  1  liter  of  water.  One  liter 
containing  36.45  grams  HC1  will  exactly  neutralize 
1  liter  containing  40  grams  NaOH. 

From  the  above  we  learn  then  that  a  normal  solu- 
tion of  an  acid  is  one  which  contains  1  gram  H  ions  per 
liter  and  a  normal  solution  of  a  base  contains  1  gram 
OH  ions  per  liter.  In  the  two  instances  cited  above 
the  norlaal  solution  corresponded  exactly  with  a 
molecular  solution  (the  molecular  weight  in  grams 
dissolved  in  a  liter). 

Suppose  we  attempt  to  make  a  normal  solution  of 
sulphuric  acid.  The  formula  is  H2SO4  and  it  dissociates 
into 

+ 

H       - 

+  /S04 
H/ 


108  ACIDS  AND  BASES 

that  is,  two  H  ions  for  every  molecule.  Then  a  normal 
solution  would  be  only  one-half  the  molecular  solution. 
An  example  of  a  base  in  which  the  same  is  true  is  cal- 
cium hydroxide1  (slaked  lime)  Ca(OH)2,  which  disso- 
ciates into 

+  /OH 

Ca<     - 

XOH. 

A  normal  solution  is  indicated  as  follows:  N/l,  twice 
normal  2N  and  half -normal  N/2.  Molecular  solutions 
are  labelled  M/l,  etc.,  and  called  molar,  half-molar,  etc. 

A  chemically  normal  solution  must  not  be  confused 
with  the  so-called  physiological  normal  saline  solution. 
The  latter  is  a  misnomer  and  instead  of  being  called 
normal  salt  solution  it  should  be  called  M/8  (eighth 
molar),  for  this  strength  of  solution  (0.9  per  cent. 
NaCl)  has  approximately  the  same  osmotic  pressure 
as  the  blood. 

Indicators. — When  acids  (which  see)  were  described 
it  was  stated  that  litmus  turns  red  in  the  presence 
of  acids  and  blue  in  the  presence  of  bases.  Therefore 
we  have  in  litmus  an  indicator  which  when  added  to  a 
solution  tells  us  whether  the  solution  is  of  acid  reac- 
tion or  basic  (alkaline)  reaction.  Paper  impregnated 
with  litmus  is  used  in  urine  analysis  to  ascertain  whether 
the  urine  is  acid  or  basic.  The  quickness  with  which 
the  strip  of  paper  turns  indicates  the  relative  strength 
of  the  acid  or  base  though  only  to  an  approximate 

1  Let  the  student  give  directions  for  preparation  of  N/l  HNOs  and 
N/l  KOH. 


POTASSIUM  109 

degree.  We  say  then  a  sample  of  urine  is  strongly  or 
weakly  acid  or  alkaline  (basic). 

Volumetric  Analysis. — Suppose  we  have  a  sample  of 
vinegar  in  which  we  want  to  determine  the  amount 
of  acid.  If  the  vinegar  is  highly  colored  we  may  dilute 
it  and  add  our  indicator.  Now  we  add  slowly  from 
a  graduated  tube  (burette)  a  normal  solution  of  a 
base  until  the  indicator  tells  us  that  the  vinegar  is  now 
no  longer  acid  but  neutral  and  1  drop  of  base  added 
brings  about  the  alkaline  color.  The  basic  solution 
being  standard  (normal)  we  know  how  much  base  is 
in  a  liter  and  any  part  of  a  liter.  Also,  we  can  calculate 
how  much  acid  will  be  neutralized  by  any  part  of  a  liter 
of  the  normal  solution  of  base.  Therefore,  reading  from 
the  burette  the  number  of  cubic  centimeters  of  base 
used  to  neutralize  the  acid  we  can  calculate  how 
much  acid  is  in  the  vinegar.  This  method  of  deter- 
mining the  strength  of  a  solution  by  testing  it  against 
a  normal  .solution  is  called  titration.  Titration  is  the 
foundation  of  volumetric  analysis.  (For  further  details 
consult  Sutton's  Volumetric  Analysis.) 

There  are  other  indicators  besides  litmus,  some  of 
which  are  acid  and  some  basic,  useful  according  to  their 
particular  properties.  The  nurse  will  employ,  besides 
litmus,  probably  only  phenolphthalein,  alizarin,  and 
Topfer's  reagent  (dimethyl-amino-azo-benzene). 

POTASSIUM,  K  (At.  wt.  =  39). 

Potassium  is  very  similar  to  sodium.  It  reacts  in 
the  same  manner  and  what  was  said  of  sodium  in  general 


110  POTASSIUM 

is  true  of  potassium.  It  is  found  as  potash  (KOH) 
in  ordinary  wood  ashes  and  the  nitrate  is  found  in 
large  deposits  (saltpetre  beds).  It  is  found  distributed 
in  the  human  body  just  as  sodium  is,  though  in  smaller 
amounts.  Potassium  salts  are  used  in  medicine  like 
sodium  salts;  practically  the  only  difference  is  that 
they  have  a  more  depressing  effect  on  the  heart  than 
the  latter. 

Lithium  is  another  metal  included  in  this  group 
with  sodium  and  potassium,  called  the  alkali  metals. 
Little  use  is  made  of  its  salts  in  modern  medicine. 

SUMMARY  OF  CHAPTER  XIX. 

An  acid  in  solution  is  dissociated  into  H  ion  +  a 
negative  ion  (e.  g.,  Cl).  A  base  in  solution  is  dissociated 
into  a  metal  (let  M  represent  any  metal)  +  OH  ion 
(hydroxyl). 

The  molecular  weight  of  HC1  is  36.458  (H  =  1.008; 
Cl  =  35.45).  In  36.458  grams  HC1  there  is  1.008  grams 
H  (approximately  1  gram).  A  normal  solution  of  an 
acid  is  a  solution  of  such  an  amount  of  the  acid  as 
would  represent  1  gram  of  ionized  H  per  liter,  in  the 
case  of  HC1  36.458  grams  per  liter.  Since  masses  of 
acids  and  bases  react  molecule  for  molecule  instead  of 
gram  for  grams,  the  amount  of  base  necessary  to  neu- 
tralize the  molecular  weight  in  grams  of  HC1,  would  be 
the  molecular  weight  of  the  base  in  grams  (NaOH  = 
40). 

A  normal  solution  of  a  base  is  such  an  amount  of 
base  as  would  represent  17  grams  (sufficient  to  combine 
with  1  gram  H)  of  hydroxyl  in  a  liter  of  water. 


SUMMARY  OF  CHAPTER  XIX  111 

Some  acids  like  H2SO4  possess  two  available  H  ions 
for  every  molecule — therefore  a  normal  solution  would 
be  half  the  gram-molecular  weight  per  liter.  This  is 
true  also  of  dihydroxy  bases  like  Ca(OH)2. 

The  term  normal  in  speaking  of  solutions  should  be 
confined  to  strictly  chemical  meaning.  Physiological 
salt  solution  is  eighth  molecular,  M/8. 

Certain  dyes  like  litmus  are  colored  differently  by 
acids  and  alkalies  (bases).  The  change  from  a  basic 
to  acid  reaction  is  accompanied  by  a  sharp  change  in 
the  color  of  the  solutions  of  the  dye.  This  color  change 
is  made  use  of  in  testing  acid  solutions  against  bases 
for  their  relative  strengths.  Such  testing  or  titration 
(titre  =  to  test)  is  known  as  volumetric  analysis.  The 
properties  and  reactions  of  potassium  resemble  those 
of  sodium. 


CHAPTER  XX. 

PHOSPHORUS— ARSENIC— ANTIMONY- 
BISMUTH. 

PHOSPHORUS  (At.  wt.  =  31). 

THE  story  of  phosphorus  forms  one  of  the  most 
interesting  chapters  in  chemistry.  Its  occurrence  in 
the  body,  its  change  of  form  and  varied  chemical 
activity  bring  it  into  prominence. 

Occurrence. — Phosphorus  occurs  as  the  phosphate 
of  calcium  Ca3(PO4)2  in  large  deposits  in  the  earth  and 
is  scattered  through  the  soil  also  in  the  form  of  salts. 
It  does  not  occur  in  the  free  state. 

The  mineral  matter  of  bones  is  largely  calcium  phos- 
phate even  to  such  an  extent  that  bone  ash  is  used  as 
a  source  for  the  preparation  of  phosphorus.  The 
tissues  of  plants  and  animals  also  contain  phosphorus 
in  various  combinations. 

Preparation. — Calcium  phosphate,  sand  (silicon  di- 
oxide) and  charcoal  (carbon)  are  heated  in  an  electric 
furnace  to  a  high  temperature  and  the  free  phos- 
phorus is  given  off.  It  is  condensed  and  purified  by 
redistillation. 

The  reaction  which  takes  place  is  an  interchange  of 
silicate  and  phosphate  and  a  reduction  of  the  phos- 
phoric acid  by  the  carbon: 

2Ca3(PO4)2  +  IOC  +  6SiO2  =  10CO  +  6CaSiO3  +  4P. 
Carbon         Calcium 
monoxide.       silicate. 


PHOSPHORUS  113 

Uses. — Until  recently  phosphorus  was  employed  in  the 
manufacture  of  matches.  On  account  of  its  poisonous 
effects  on  workmen  its  use  now  is  forbidden  by  law. 
Phosphorus  is  used  in  rat  poison  and  vermin-killer. 
In  rare  instances  it  is  sometimes  administered  as  a 
therapeutic  agent.  The  hypophosphites  were  formerly 
administered  as  tonics  though  now  it  is  believed  that 
such  treatment  is  worthless.  The  pentoxide  (P2O5)  is 
a  strong  dehydrating  agent  and  the  chlorides  PC13  and 
PC15  are  used  in  building  up  certain  organic  (carbon- 
hydrogen)  compounds. 

Properties. — Cold  phosphorus  is  a  yellowish,  brittle 
solid.  On  being  warmed  to  room  temperature  it 
becomes  soft  and  waxy  and  melts  at  a  little  above 
body  temperature  (45°  C.).  The  free  elements  may 
exist  in  four  different  states:  as  yellow  phosphorus 
(ordinary  form) ;  red  phosphorus;  black  phosphorus,  and 
white  phosphorus.  The  first  two  are  more  important 
from  a  chemical  stand-point  and  more  is  known  of 
them. 

Yellow  phosphorus  is  so  active  that  it  must  be  kept 
under  water.  When  oxygen  comes  in  contact  with  it, 
some  of  the  oxygen  is  converted  into  ozone,  and  there 
is  also  a  chemical  union  of  phosphorus  and  oxygen  in 
which  the  oxide  is  formed,  heat  is  liberated  and  the 
phosphorus  glows.  Undoubtedly  the  property  which 
phosphorus  possesses  of  glowing  in  the  dark  is  in  some 
way  associated  with  oxidation.  When  the  temperature 
reaches  50°  C.,  the  phosphorus  in  contact  with  oxygen 
takes  fire.  Yellow  phosphorus  is  very  active  chemi- 
cally, forming  some  of  the  compounds  which  will  later 
8 


114  ARSENIC 

be  discussed.  If  yellow  phosphorus  is  heated  in  some 
inert  gas  like  nitrogen  to  250°  it  is  changed  to  a  red 
amorphous  powder  known  as  red  phosphorus.  In  this 
form  phosphorus  is  not  so  active.  It  does  not  combine 
readily  with  other  elements  and  does  not  take  fire 
when  heated  in  the  presence  of  oxygen.  It  is  much 
less  poisonous  than  yellow  phosphorus. 

Yellow  phosphorus  combines  with  hydrogen  to 
form  phosphine  PH3,  a  gas,  and  P2H,  a  solid.  It  also 
combines  with  oxygen  to  form  oxides  P2O3  and  P2O5, 
and  with  hydrogen  and  oxygen  to  form  acids.  Phos- 
phoric acid  H3PC>4,  which  combines  with  bases  to  form 
phosphates  and  hypophosphorous  acid  H3P02,  which 
in  like  manner  forms  hypophosphites,  are  the  more 
important. 

A  group  of  important  substances  found  in  yolk  of 
eggs,  in  milk  and  in  brain  tissues,  known  as  lecithins 
contain  phosphoric  acid,  combined  with  acids  from 
fats  and  an  organic  base. 

ARSENIC  (At.  wt.=  75). 

Arsenic  in  some  cases  acts  like  phosphorus  and  in 
others  like  sulphur.  It  occurs  in  combinations  in 
nature,  never  free.  Its  chief  source  is  the  iron  com- 
pound Fe2As3,  and  it  also  occurs  in  a  compound  similar 
to  Fool's  gold  (pyrites). 

Arsenic  is  a  gray,  hard,  brittle  metal.  It  combines 
with  various  elements:  hydrogen,  oxygen,  sulphur, 
the  halogens  and  the  metals.  Its  hydrogen  compound 
reminds  us  of  phosphine.  Arsine  AsII3  is  formed  when 


ANTIMONY  115 

hydrogen  is  generated  in  a  solution  containing  arsenic. 
This  is  the  basis  of  the  well-known  Marsh  test  for 
arsenic.  The  solution  under  suspicion  as  containing 
arsenic  is  allowed  to  run  into  a  flask  where  hydrogen 
is  being  produced  by  the  action  of  sulphuric  acid  on 
zinc.  The  nascent  hydrogen  reacts  with  the  arsenic 
to  form  arsine  which  comes  out  the  delivery  tubes 
with  the  excess  of  hydrogen.  The  jet  from  the  delivery 
tube  is  lighted  and  a  cold  porcelain  dish  held  in  the 
small  flame.  If  arsine  is  present  a  metallic  film  of 
arsenic  is  deposited  on  the  dish. 

Fowler's  solution  is  a  solution  of  potassium  arsenite : 
K2HAsO3  formed  by  boiling  arsenic  trioxide  with 
potassium  acid  carbonate. 

As2O3  +  4KHCO3  =  2K2HAsO3. 

Arsenic  has  come  into  prominence  lately  on  account 
of  its  part  in  the  composition  of  salvarsan  which  is 
an  elaborated  arsenic  and  benzene  compound. 

Arsenic  is  a  common  impurity  of  mineral  acids  and 
certain  salts.  Special  methods  are  necessary  to  rid 
them  of  the  last  traces  of  this  metal  and  the  standards 
set  by  the  Pharmacopoeia  allow  only  minute  amounts 
of  arsenic  as  impurity. 


ANTIMONY,  Sb.  (At.  wt.  =  120). 

Antimony  is  very  much  like  arsenic:  one  seldom 
attempts  to  remember  its  properties  except  that  they 
are  almost  the  same  as  arsenic.  Even  the  Marsh  test 
with_slight  variation  is  used  as  a  test  for  antimony. 


116  BISMUTH 

Our  interest  in  this  metal  lies  in  the  fact  that  it  is 
one  of  the  chief  components  of  tartar  emetic  which 
is  potassium  and  antimony  tartrate.  Tartar  emetic  is 
put  in  compound  syrup  of  squills. 

Antimony  is  useful  in  making  the  alloy  used  for 
manufacturing  type. 

BISMUTH,  Bi.  (At.  wt.=208). 

Bismuth  is  also  like  arsenic  and  closely  allied  in 
properties  to  phosphorus  and  antimony.  .It  is  not  so 
active  chemically  as  the  other  members  of  the  group. 
In  fact  it  is  found  free  in  nature.  Bismuth  is  a  crystal- 
lized solid  but  has  not  as  much  of  the  metallic  sheen 
as  arsenic  and  antimony. 

Various  salts  exist.  Their  formulas  are  easily  pre- 
dicted when  we  know  that  bismuth  is  trivalent,  that 
is,  one  atom  will  hold  in  combination  three  atoms 
of  a  monovalent  element  like  chlorine.  Bismuth 
hydroxide  is  Bi(OH)3  and  the  nitrate  is  Bi(NO3)3. 
There  is  a  combination  of  these  two  salts  called  the 
subnitrate  Bi(OH)2NO3  in  which  it  will  be  seen  that 
the  bismuth  is  not  entirely  nitrated  but  that  two  of 
the  nitrate  groups  (NO3)  are  replaced  by  hydroxyl 
groups  (OH).  On  account  of  these  two  hydroxyl 
groups  in  the  molecule  the  salt  will  react  basic  (alkaline) 
and  is  called  the  basic  nitrate. 

Other  metals  are  capable  of  forming  subnitrates 
(and  other  basic  salts)  also.  Bismuth  salts  are  used 
as  astringents  and  in  axray  work.  If  the  salts  are  taken 
into  the  intestine  and  an  x-ray  made  it  is  found  that 


SUMMARY  OF  CHAPTER  XX  117 

the  rays  are  obstructed  by  the  bismuth  and  shadows 
are  cast  on  the  plate.  In  this  manner  the  movements 
and  the  shape  of  the  stomach  and  intestines  are  studied. 
Sinuses  may  be  studied  in  like  manner. 

SUMMARY  OF  CHAPTER  XX. 

Phosphorus  is  a  yellowish,  brittle  solid  which  becomes 
waxy  on  heating.  It  may  exist  in  four  forms:  yellow, 
red,  black  or  white.  Yellow  phosphorus  is  the  most 
common.  This  variety  is  the  most  active  chemically. 
It  glows  in  air  and  may  burn  spontaneously  if  not 
covered  with  water.  Yellow  phosphorus  is  changed  into 
an  inert  form  (red  phosphorus)  on  heating  in  an  inert 
gas  like  nitrogen. 

Phosphorus  occurs  as  calcium  phosphate  in  mineral 
deposits  and  in  this  form  also  constitutes  the  chief 
inorganic  part  of  bone.  The  element  is  obtained  from 
this  salt  by  heating  it  in  an  electric  furnace  with  a 
mixture  of  sand  and  charcoal. 

Phosphorus  combines  with  hydrogen  to  form  phos- 
phine  PH3  and  with  oxygen  and  water  to  form  several 
phosphoric  acids.  The  salts  of  these  acids  are  called 
phosphites,  hypophosphites,  phosphates,  etc. 

An  important  class  of  foodstuffs,  lipoids  (fat-like 
substances)  may  contain  phosphorus  in  combination. 
Lecithin  found  in  eggs,  milk,  and  brain  tissue  is  a 
phosphorus  containing  lipoid. 

Arsenic  is  very  similar  to  phosphorus  in  its  com- 
pounds. It  is  less  active  chemically  and  the  free 
element  possesses  more  metallic  properties.  It  forms 
arsine  with  hydrogen  (similar  to  phosphine)  and  also 


118  BISMUTH 

forms  acids  and  salts,  arsenites,  arsenates,  analogous 
to  phosphorus  compounds.  The  Marsh  test  depends 
upon  the  formation  of  arsine,  AsH3.  Arsenic  com- 
pounds produce  acute  and  chronic  stages  of  poisoning. 
Some  compounds,  potassium  arsenite,  are  adminis- 
tered, and  many  of  the  newer  products  of  chemo- 
therapy contained  arsenic  combined  with  organic 
radicals  (salvarsan). 

Antimony  is  similar  to  phosphorus  and  arsenic. 
Potassium  and  antimony  tartrate  is  the  principal 
medicinal  preparation.  Bismuth  belongs  to  the  same 
chemical  group.  It  is  a  metal,  sometimes  found  free 
in  nature.  The  element  is  trivalent,  i.  e.,  holds  in  com- 
bination three  chlorine  atoms  or  hydroxyl  groups 
(BiCl3,  Bi(OH)s).  The  nitrate  Bi(NO3)3  and  especially 
the  subnitrate  (Bi(OH)(NO3)2,  also  the  sub-gallate 
are  used  in  local  applications  for  their  astringent  effect. 
Bismuth  salts  are  relatively  impervious  to  Rontgen 
rays  and,  hence,  find  use  in  rontgenography. 


CHAPTER  XXI. 

CALCIUM. 

(At.  wt.=40.) 

SODIUM,  potassium  and  lithium  are  called  the 
alkali  metals  on  account  of  their  ability  to  form  bases 
(alkalies).  Calcium,  strontium  and  barium  also  pos- 
sess basic  qualities  but  not  to  the  same  extent.  This 
group  is  called  the  alkaline  earths.  Calcium  will  be 
discussed  as  the  most  interesting  representative  of 
the  group.  Barium  is  used  little  in  medicine,  and  only 
one  salt  of  strontium  need  be  known,  viz.,  strontium 
bromide. 

Occurrence. — Limestone  and  chalk  are  impure  cal- 
cium carbonate.  Marble  is  a  pure  crystallized  lime- 
stone. The  calcium  phosphate  beds  have  been  men- 
tioned under  phosphorus  and  fluorite  (CaF2)  under 
fluorine. 

Lime. — It  has  already  been  stated  (Chapter  I)  that 
lime  results  from  the  heating  of  limestone.  The  reac- 
tion is  very  simple,  carbon  dioxide  is  given  off. 

CaCO3  =  CaO  +  CO2. 

If  the  gas  be  kept  confined  in  the  chamber  with  the 
lime  it  will  recombine  on  cooling.  This  is  one  of  the 
simplest  examples  of  a  reversible  reaction. 


120  CALCIUM 

When  water  is  poured  on  lime  slaking  takes  place 
with  the  evolution  of  heat.  . 

CaO  +  H.OH  =  Ca(OH)2. 

In  solution  calcium  hydroxide  dissociates  into  Ca, 

OH,OH  and  is  therefore  basic. 

Bleaching  Powder. — Reference  to  bleaching  powder 
has  already  been  made  in  connection  with  chlorine. 
Chlorine  gas  passed  over  moist  lime  forms  equal 
parts  of  CaCl2  and  calcium  hypochlorite  Ca(OCl)2  or 
one  compound: 

0  /oci 
Ca<cl 

According  to  Jones  it  is  the  latter  toward  which  most- 
things  point. 

Whatever  the  exact  composition  of  bleaching  powder 
may  be,  it  is  the  most  convenient  means  of  trans- 
porting chlorine,  for,  all  the  chlorine  which  goes  into 
the  reaction  is  recovered  when  the  bleaching  solution 
is  rendered  acid.  Even  a  weak  acid  like  carbonic  suf- 
fices to  replace  the  chlorine  forming  calcium  carbonate. 
For  this  reason  bleaching  powder  exposed  to  the  air 
over  long  periods  loses  its  characteristics  because  of  the 
C02  in  the  air. 

Plaster  of  Paris. — Calcium  sulphate  crystallizes  with 
two  parts  of  water  of  crystallization,  CaSO4.2  H2O. 
If  the  crystals  are  heated  slightly  above  the  boiling 
point  of  water  (107°)  only  a  part  of  the  water  is  lost 
forming  the  compound 


SUMMARY  OF  CHAPTER  XXI  121 

This  is  plaster  of  Paris.  When  water  is  added  the 
compound  CaSO4.2H2O  is  rebuilt  and  the  crystals 
fuse  together  and  harden  (set)  into  a  mass.  If  all 
the  water  is  driven  off  in  the  preparation  of  plaster 
of  Paris  (i.  e.,  heated  too  high)  the  hydration  (adding 
of  water)  takes  place  too  slowly  to  be  of  use.  It  will 
be  remembered  that  plaster  of  Paris  is  used  in  the 
making  of  splints.  The  student  now  understands  why 
it  must  be  worked  quickly  after  the  water  is  added. 

Calcium  Chloride. — Calcium  chloride  has  a  great 
attraction  for  water  and  is  therefore  useful  to  the 
chemist  as  a  dehydrating  agent.  Salts  absorbing  water 
on  exposure  to  the  air  are  said  to  be  hygroscopic. 

Acetylene. — Acetylene  lamps  are  well  known.  Acety- 
lene is  a  compound  of  hydrogen  and  carbon  which 
burns  with  a  brilliant  light.  Acetylene  is  manufac- 
tured by  allowing  water  to  come  into  contact  with 
calcium  carbide  CaC2. 

CaC2  +  H2O  =  CaO  +  C2H2. 

Acetylene. 

Calcium  carbide  is  made  by  heating  a  mixture  of 
lime  and  powdered  charcoal  in  an  electric  furnace. 

Flame  Tests. — A  small  amount  of  a  calcium  salt 
introduced  into  the  flame  of  a  Bunsen  burner  produces 
a  dark  red  color.  Strontium  salts  impart  a  brilliant  red 
and  barium  salts  a  green  color  to  the  flame. 

SUMMARY  OF  CHAPTER  XXL 

Calcium,  strontium  and  barium  have  certain  char- 
acteristics in  common:  their  carbonates  and  sulphates 


122  CALCIUM 

are  relatively  less  soluble  in  water  and  all  three  form 
hydroxides  which  are  more  or  less  alkaline.  These 
elements  are  bivalent  and  constitute  a  group  in  the 
periodic  system  known  as  the  alkaline  earths.  The 
hydroxides  of  the  alkaline  earths  are  not  so  strongly 
basic  in  character  as  the  alkali  metal  hydroxides. 

Calcium  is  the  most  important  member  of  the  group. 
It  does  not  occur  free  in  nature,  but  its  salts  espe- 
cially the  carbonate  and  phosphate  are  very  common. 
Marble  is  crystallized  calcium  carbonate.  Lime  is 
CaO.  It  results  from  the  intense  heating  of  CaCO3. 
Water  slaking  means  the  addition  of  water  to  CaO, 
forming  Ca(OH)2  (calcium  hydrate). 

Bleaching  powder 


Ca< 


OCl 
Cl 


is  formed  by  passing  chlorine  gas  over  lime.  It  is 
the  most  economical  and  convenient  method  of  trans- 
porting chlorine  for  bleaching  and  disinfecting  pur- 
poses. Acids  liberate  chlorine  from  bleaching  powder. 

Plaster  of  Paris  is  calcium  sulphate  only  partially 
hydrated.  When  water  is  added  to  a  paste  of  plaster 
of  Paris  full  hy  drat  ion  quickly  results  and  calcium 
sulphate  crystals  (CaS04.2H20)  form  (setting). 

Salts  like  calcium  chloride  which  absorb  water  from 
the  air  are  said  to  be  hygroscopic. 

Acetylene  is  formed  by  the  action  of  water  on  cal- 
cium carbide. 

Calcium  salts  impart  a  dull  red,  strontium  salts 
a  brilliant  red,  and  barium  salts  a  green  color  to  the 
Bunsen  flame. 


CHAPTER  XXII. 
MAGNESIUM  GROUP. 

MAGNESIUM  (At.  wt.  =  25). 

MAGNESIUM,  zinc,  mercury,  cadmium  and  glucinum 
belong  to  this  group.  Magnesium  is  of  greatest  impor- 
tance, especially  from  the  stand-point  of  therapeutics. 
It  occurs  in  nature  as  the  carbonate,  the  chloride, 
the  silicate,  and  the  sulphate.  One  of  the  chief  con- 
stituents of  asbestos  is  magnesium  silicate.  Epsom 
salt  is  magnesium  sulphate.  The  element  magnesium, 
which  can  be  obtained  by  electrolysis  of  its  salts  is 
a  white,  very  light  metal.  It  burns  in  air  with  a 
brilliant,  white  light,  and  for  this  reason  is  used  exten- 
sively in  fire-works. 

The  Flame  Test. — Just  as  metallic  magnesium  burns 
characteristically  in  air  other  metals  like  sodium  and 
potassium  can  be  identified  by  their  action  in  a  flame. 
Sodium  burns  with  a  bright,  yellow  light  and  potassium 
gives  the  flame  a  peach-blossom  color.  Many  metals, 
for  example,  iron,  will  not  burn  unless  powdered  and 
dusted  into  a  flame,  but  if  a  piece  be  heated  white  hot 
and  placed  in  an  atmosphere  of  pure  oxygen  it  will 
burn  brilliantly.  In  testing  the  various  elements  it 
is  not  essential  that  they  be  in  the  free  state.  For 
example,  any  salt  of  sodium  will  color  a  flame  yellow; 


124  MAGNESIUM  GROUP 

potassium  salts  also  yield  the  characteristic  peach- 
blossom  color,  strontium  salts  impart  brilliant  red; 
calcium  a  dull  red,  barium  and  copper,  green,  to  the 
flame.  If  the  light  from  the  flame  in  which  any  salt 
is  placed  is  conducted  through  a  prism  in  such  a  manner 
as  to  resolve  it  into  its  primary  colors  characteristic 
bands  of  different  colors  will  appear.  This  is  known  as 
spectrum1  analysis.  By  these  means  the  various  ele- 
ments have  been  detected  in  the  sun  and  stars. 

Magnesia. — When  metallic  magnesium  is  burned 
magnesium  oxide,  MgO,  is  formed.  This  compound 
is  what  is  known  as  magnesia.  It  is  insoluble  in 
water,  but  when  mixed  with  water  to  form  a  cream  it 
forms  the  well-known  milk  of  magnesia. 

Magnesia  is  generally  made  by  heating  the  carbonate. 
The  CO2  is  driven  off  leaving  MgO. 

MgCOs  =  MgO  +  CO2. 

Problem  for  student:  What  is  the  chemical  reaction 
when  milk  of  magnesia  is  taken  into  the  stomach  where 
free  hydrochloric  exists?  MgO  +  2HC1=  ? 

Why  do  you  write  two  parts  HC1? 

Epsom  Salt. — Epsom  salt  as  found  in  the  Epsom 
springs,  is  magnesium  sulphate.  It  crystallizes  with 
seven  parts  water  of  crystallization,  MgSO4.7H2O. 
There  is  a  mineral  consisting  of  MgS04.H2O. 


1  A  beam  of  white  light  passing  through  a  prism  is  spread  out  into 
the  colors  of  the  rainbow — violet,  indigo  blue,  green,  yellow,  orange, 
and  red.  All  these  colors  together  are  called  the  spectrum,  and  the 
instrument  for  observing  this  phenomenon  and  the  various  bands 
formed  by  different  elements  is  called  a  spectroscope.  The  elements 
in  a  molten  condition  produce  characteristic  lines  in  the  spectrum. 


MERCURY  125 

When  magnesium  sulphate  is  dissolved  in  water 
it  absorbs  heat  and  makes  the  solution  cold,  thus 
reducing  the  solubility.  In  making  strong  solutions, 
therefore,  warm  water  should  be  used. 

MERCURY,  Hg.  (At.  wt.=200). 

Mercury  is  the  only  metal  which  exists  in  the  liquid 
state  at  ordinary  temperatures.  It  occurs  free  in 
nature  and  is  separated  from  the  substances  with  which 
it  is  found  by  distillation. 

On  account  of  the  fact  that  it  solidifies  at  a  very 
low  temperature,  and  also  that  its  volume  is  changed 
to  a  considerable  extent  when  its  temperature  is  varied, 
it  is  very  useful  for  making  thermometers. 

Amalgams. — When  mercury  and  gold  come  into 
contact  they  combine— the  gold  loses  its  yellow  color 
and  seems  to  be  silvered  over.  If  there  is  an  excess 
of  mercury  the  gold  will  dissolve  in  it.  The  same  is 
true  of  silver,  magnesium,  calcium,  and  other  metals. 
The  combination  of  any  of  these  metals  with  mercury 
is  called  an  amalgam.  Sodium  and  potassium  form 
amalgams  with  mercury  which  are  solid  at  ordinary 
temperatures  and  offer  a  very  convenient  method  of 
applying  the  alkali  metals  for  chemical  reactions. 
The  amalgamating  property  of  mercury  is  made  use  of 
in  the  recovery  of  gold  and  silver  in  certain  mining 
processes. 

Salts  of  Mercury. — Mercury  is  an  example  of  an 
element  which  possesses  a  variable  valence;  that  is  to 
say,  mercury  salts  exist  in  which  the  mercury  ion  has 


126  MAGNESIUM  GROUP 

+ 
valence  of  one  (Hg),  there  are  also  those  salts  in  which 

the  mercury  ion  has  a  valence  of  two  (Hg). 

This  property  of  variable  valence  is  best  illustrated 
by  the  chlorides.  Mercury  chloride  (HgCl)  is  calomel, 
a  white,  non-crystalline  insoluble,  non-poisonous, 
powder.  Here  one  readily  sees  the  mercury  ion  has 
in  combination  one  ion  of  chlorine  and  is  therefore 
monovalent.  Mercury  bichloride  (HgCl2)  is  corrosive 
sublimate,  a  crystalline,  soluble  intensely  poisonous 
solid.  The  mercury  ion  in  this  compound  holds  in 
combination  two  chlorine  ions  and  is  therefore  biva- 
lent. In  compounds  like  HgCl,  Hg2O,  Hgl,  etc., 
where  the  Hg  ion  is  monovalent  the  mercury  is  said 
to  be  in  the  mercurous  condition.  The  compounds 
mentioned  then  would  be  called  mercurous  chloride, 
mercurous  oxide,  and  mercurous  iodide.  Such  com- 
pounds as  HgCl2,  HgO,  HgI2  are  called  mercuric  com- 
pounds (mercuric  chloride,  mercuric  oxide,  mercuric 
iodide). 

The  striking  difference  between  mercurous  and  mer- 
curic iodide  is  worthy  of  comment;  mercurous  iodide 
is  bright  yellow,  mercuric  iodide  is  scarlet  red. 

Both  mercurous  and  mercuric  compounds  are 
employed  extensively  in  medicine  and  surgery.  The 
student  should  be  thoroughly  familiar  with  the  two 
chlorides,  especially  since  the  substitution  of  one  for 
the  other  is  a  very  dangerous  error. 

On  standing  exposed  to  light,  calomel  becomes  dark, 
owing  to  reduction  and  deposit  of  metallic  mercury. 
Obviously  at  this  stage  it  should  not  be  administered. 


SUMMARY  OF  CHAPTER  XXII  127 

Ammoniated  mercury  which  is  the  principal  con- 
stituent of  Ammoniated  Mercury  Ointment  is  a  mer- 
curic compound  in  which  one  Cl  is  replaced  by  NH2. 
Instead  of 


the  formula  then  is 

Jig  <C  -NTTT 

JNX12. 

It  is  made  by  mixing  a  solution  of  bichloride  and 
ammonia  water  when  a  white  precipitate  of  ammo- 
niated  mercury  is  formed.  When  ammonia  is  added 
to  a  mercurous  salt  a  black  precipitate  is  formed.  This 
is  a  simple  method  for  ascertaining  whether  a  given 
mercury  compound  is  a  mercurous  or  a  mercuric 
compound. 

SUMMARY  OF  CHAPTER  XXII. 

To  the  magnesium  group  belong  magnesium,  zinc, 
mercury,  cadmium  and  glucinum.  The  most  impor- 
tant member  of  the  group  for  the  nurse  is  magnesium, 
though  mercury  warrants  description. 

Magnesium  occurs  as  the  sulphate,  the  chloride,  and 
the  silicate.  Epsom  salt  is  the  sulphate  and  asbestos 
is  the  silicate. 

Metallic  magnesium  is  light  in  weight  and  color.  It 
burns  in  air  with  a  brilliant,  white  light,  forming  MgO; 
the  substance  when  mixed  with  water  is  known  as  the 
milk  of  magnesia.  Magnesium  oxide  in  the  stomach 
is  converted  into  MgCb 

The  spectroscope  is  an  instrument  for  viewing  the 
characteristic  lines  produced  by  molten  metals  or 


128  MAGNESIUM  GROUP 

their  salts.  By  spectrum  analysis  elements  may  be 
detected  in  the  sun. 

The  only  metal  liquid  at  ordinary  temperature  is 
mercury,  which  occurs  free  in  nature  and  is  recovered 
by  distillation. 

Amalgams  are  combinations  of  various  metals  like 
sodium,  potassium,  gold,  and  silver  with  mercury. 

Mercury  may  be  monovalent  or  bivalent.  Calomel 
is  the  monochloride  (HgCl)  in  which  the  mercury  is 
monovalent  (in  the  mercurous  state).  Corrosive 
sublimate  is  mercuric  chloride  HgCl2  in  which  the 
mercury  is  bivalent.  The  differences  between  these 
salts  are  very  important. 

A  convenient  test  for  mercurous  and  mercuric  salts 
is  the  addition  of  ammonia ;  mercurous  salts  are  turned 
black;  solution  of  mercuric  salts  yield  a  white  precipi- 
tate on  the  addition  of  ammonia. 


CHAPTER  XX111. 
ALUMINUM— IRON— MANGANESE. 

ALUMINUM,  Al.  (At.  wt.=27). 

THE  remarkably  light  metal  aluminum  is  the  element 
aluminum  in  the  free  state.  This  is  an  interesting 
metal  from  the  stand-point  of  general  knowledge.  It 
suffices  here  to  state  that  clay  is  an  impure  aluminum 
silicate  which  may  vary  in  properties  and  uses  accord- 
ing to  its  impurities.  Aluminum  hydroxide  (A1(OH)3) 
is  used  for  clarifying  solutions,  and  the  class  of  com- 
pounds known  as  the  alums  are  useful  as  styptics 
and  astringents.  The  commonest  representative  of 
the  alums  is  potassium  alum  (ordinary  alum),  which 
is  a  compound  of  potassium  and  aluminum  sulphate 
(A1-K-(SO4)2.12H2O)  plus  twelve  parts  of  water  of 
crystallization. 

IRON  (FERRUM),  Fe.  (At.  wt.=56). 

Chemically  and  industrially  iron  is  one  of  the  most 
important  elements.  It  plays  an  essential  role  in 
the  living  organism  but  a  thorough  knowledge  of  its 
salts  is  not  required  of  the  nurse.  Only  a  few  facts 
may  be  related. 

The  essential  coloring  matter  of  the  red-blood  cells 
is  an  iron  compound.  Iron  is  also  found  in  bone. 
9 


130  IRON 

Certain  foods,  like  spinach  and  kale,  are  said  to  contain 
this  element  in  larger  amounts  than  other  foods  and, 
hence,  are  useful  in  furnishing  a  deficient  organism  with 
this  essential  element. 

Iron,  like  mercury,  has  a  variable  valence,  and  exists 
in  combination  in  the  ferrous  or  ferric  state.  Thus 
Fe(OH)2  is  ferrous  hydroxide,  FeCl2  ferrous  chloride; 
while  Fe(OH)3  is  ferric  hydroxide,  and  FeCl3  ferric 
chloride.  The  ferric  salts  are  the  more  stable  as  the 
ferrous  compounds  are  easily  oxidized  into  the  ferric 
variety.  It  has  been  found  that  the  change  from  ferric 
to  ferrous  is  a  reduction  process  and,  conversely, 
from  ferrous  to  ferric  an  oxy dative  reaction;  also  the 
difference  in  the  Fe  ion  is  one  of  electrical  charge. 

There  are  about  twenty-four  official  preparations 
of  iron  in  the  Pharmacopoeia  which  may  be  said  to  be 
primary  and  eleven  more  made  from  these.  The 
chemistry  of  these  compounds  can  be  readily  under- 
stood from  what  has  already  been  learned  about  chemi- 
cal processes  in  general.  One  important  preparation  is 
the  so-called  arsenic  antidote  which  is  a  mixture  of 
magnesia  and  ferric  hydroxide.  The  arsenic  is  precip- 
itated by  this  mixture  probably  in  the  form  of  ferric 
and  magnesium  arsenite  which  is  insoluble  and  can 
then  be  washed  out  of  the  stomach. 

The  preparation  is  made  by  mixing  a  solution  of 
ferric  sulphate  (40  parts  ferric  sulphate  in  125  parts  of 
water)  together  with  a  thin  paste  consisting  of  10  parts 
of  magnesium  oxide  in  750  parts  water.  These  two 
preparations  should  be  kept  made  up  separately  ready 
for  mixing. 


SUMMARY  OF  CHAPTER  XXIII  131 

MANGANESE,  Mn.  (At.  wt.  =  55). 

Manganese  dioxide,  Mn02,  has  already  been  referred 
to  as  an  oxidizing  agent.  Manganese  forms  a  great 
variety  of  compounds  for  the  reason  that  it  can  exist 
in  so  many  states  of  valence.  It  forms  salts  just  as 
iron  does  and,  on  the  other  hand,  enters  into  combina- 
tions to  form  negative  ions.  Potassium  permanganate 
KMnO4  is  an  example  of  the  latter.  This  compound 
loses  its  oxygen  easily  in  either  acid  or  alkaline  solution. 
In  contact  with  organic  matter  solutions  of  perman- 
ganate are  reduced  and  lose  the  characteristic  purple 
color,  becoming  a  dirty  brown.  On  account  of  its 
oxidizing  power,  permanganate  is  .slightly  antiseptic. 
It  is  used  in  medicine  as  an  irrigant. 

SUMMARY  OF  CHAPTER  XXIII. 

Aluminum  is  one  of  the  lightest  metals  known.  Its 
strength  is  out  of  proportion  to  its  weight.  The  free 
element  does  not  occur  in  nature  but  its  silicate  (clay)  is 
abundant.  It  is  separated  from  its  compounds  with 
great  difficulty.  However,  electrochemistry  has  made  it 
possible  in  recent  years  to  produce  aluminum  at  low 
cost. 

The  chief  compounds  of  interest  here  are  the  hydrox- 
ide A1(OH)3,  which  is  used  for  clarification  purposes 
and  the  alums.  Ordinary  alum  is  a  double  sulphate  of 
aluminum  and  potassium  (A1K(SO4)2.12H2O),  and  is 
a  representative  of  a  type  of  double  sulphates.  There 
are  also  chromium  alums  and  iron  alums  in  which  the 


132  MANGANESE 

aluminuni  is  replaced  by  chromium  or  iron  as  the  case 
may  be. 

Iron  is  a  very  important  element  both  from  an  indus- 
trial and  a  biological  view  point.  The  red  coloring 
matter  of  the  blood  contains  iron. 

Iron  occurs  free  in  nature  and  is  found  extensively 
as  the  oxide. 

Iron  has  a  variable  valence — it  may  be  bivalent  or 
trivalent. 

The  ferric  compounds  are  more  stable  than  the  ferrous 
compounds. 

Arsenic  antidote  is  a  mixture  of  magnesia  and  ferric 
hydroxide. 

Manganese  salts  are  very  numerous  because  of  the 
variable  valence  of  the  element. 

Manganese  dioxide  MnO2  and  potassium  perman- 
ganate KMn(>4  are  oxidizing  agents.  The  latter  in 
weak  solution  is  an  astringent. 


CHAPTER  XXIV. 
LEAD— SILVER— PLATINUM. 

LEAD  (PLUMBUM),  Pb.  (At.  wt.  =  207). 

THE  heaviness  of  lead  is  proverbial  though  its  specific 
gravity  (11.4)  is  slightly  less  than  mercury  (13.9). 
Lead  is  bivalent  and  forms  salts  like  PbC^.  One  of 
the  most  important  salts  in  medicine  is  the  acetate 

CH3COO\ 

>Pb 

CHsCOCK 

the  so-called  sugar  of  lead,  useful  in  skin  diseases. 
Lead  is  slightly  soluble  in  pure  water  and  more  soluble 
in  water  in  which  vegetation  has  fermented.  Since 
even  small  amounts  of  lead  taken  into  the  body  accu- 
mulate there  and  finally  cause  lead  poisoning  (plum- 
bism)  it  is  unsafe  to  use  lead  pipes  for  conducting 
drinking  water. 

SILVER  (ARGENTUM),  Ag.  (At.  wt.  =  108). 

Silver  is  moderately  resistant  to  chemical  action 
but  is  attacked  readily  by  nitric  acid  which  converts 
it  into  silver  nitrate  (lunar  caustic  AgN03).  Silver 
nitrate  is  reduced  when  it  comes  into  contact  with 
organic  matter  and  metallic  silver  is  deposited.  This 


134  PLATINUM 

is  the  reason  that  one's  fingers  are  blackened  by  hand- 
ling it.  Silver  nitrate  forms  compounds  with  albumins, 
e.  g.,  argyrol,  which  are  used  in  the  treatment  of 
infections  of  mucous  membranes. 

The  halogen  compounds  with  silver,  especially  silver 
bromide,  darken  on  exposure  to  light  and  for  this 
reason  are  used  to  manufacture  sensitized  plates  for 
photography.  When  light  strikes  these  plates  some 
slight  change  is  produced  according  to  the  intensity 
and  duration  of  the  light.  When  this  plate  is  put  in 
some  reducing  agent  like  pyrogallic  acid  ("developer") 
metallic  silver  is  deposited  where  the  light  has  affected 
the  changes.  This  deposit  of  metallic  silver  will  of 
course  form  shadows  of  varying  degree.  The  unchanged 
silver  bromide  must  be  dissolved  away  before  the 
other  light  comes  into  contact  with  the  plate.  This 
is  done  by  washing  in  sodium  hyposulphite,  Na2S2O3 
("fixing"  in  "hypo").  The  plate  is  washed  again  in 
water  and  dried.  This  "negative"  is  used  to  "print" 
the  image  on  sensitized  paper  which  is  "developed" 
and  "fixed"  in  the  same  manner  as  the  plate. 

PLATINUM,  Pt.  (At.  wt.  =  195). 

Platinum  on  account  of  its  usefulness  and  rare 
occurrence  is  worth  more  than  gold.  It  is  very  highly 
resistant  to  chemical  action  and  for  this  reason  is  very 
useful  in  chemical  procedures.  It  may  be  heated  in 
the  air  without  being  oxidized,  hence  the  platinum 
needles  with  which  the  bacteriologist  transfers  cultures. 
On  account  of  its  high  melting  point  and  freedom  from 


SUMMARY  OF  CHAPTER  XXIV  135 

oxidation,  contact  points  for  electrical  apparatus  are 
made  of  platinum.  Points  and  knives  for  thermo- 
cautery  are  also  made  of  platinum. 

The  action  of  platinum  in  a  finely  divided  state  in 
bringing  about  chemical  reaction  (catalyzer)  has 
already  been  mentioned.  Platinum  chloride,  PtCU,  is 
used  also  as  a  catalyzer;  for  example,  in  the  produc- 
tion of  hydrogen  by  the  action  of  HC1  or  Zn,  a  small 
amount  of  PtCl4  greatly  accelerates  the  reaction. 

Colloids. — Platinum  is  insoluble  in  water  but  if  a 
strong  current  is  allowed  to  pass  between  two  plati- 
num points  in  water,  some  of  the  metal  goes  into  minute 
suspension  in  particles  so  small  that  they  cannot  be 
seen  under  a  microscope.  This  is  colloidal  suspension. 
Only  crystalloids  (substances  which  can  be  crystal- 
lized) go  into  true  solution.  A  colloidal  suspension 
lies  between  a  true  solution  and  a  fine  suspension. 
Colloids  are  precipitated  by  boiling  with  acids.  Other 
metals,  as  silver,  gold,  copper,  etc.,  can  be  transformed 
into  the  colloidal  state.  These  facts  are  related  to 
give  the  student  some  sort  of  an  idea  of  what  is  meant 
by  the  term  colloid  for  many  of  the  vital  reactions  of 
the  cell  life  are  now  explained  in  terms  of  colloids. 

SUMMARY  OF  CHAPTER  XXIV. 

Silver  and  lead  are  very  similar  chemically.  Both 
are  fairly  resistant  to  chemical  action;  nitric  acid, 
however,  attacks  both,  forming  nitrates. 

Sugar  of  lead  is  lead  acetate  Pb(OOC.CH3)2.  Lead 
is  bivalent. 


136  PLATINUM 

Metallic  lead  is  slightly  soluble  in  pure  water  and 
more  soluble  in  slightly  acidulated  water.  Lead  poison- 
ing may  result  from  the  consumption  of  water  con- 
ducted in  lead  pipes. 

Silver  salts  as  well  as  lead  are  astringent.  Silver 
nitrate  and  silver  albuminates  are  used  in  the  treat- 
ment of  certain  infections. 

Silver  salts  find  extensive  use  in  photography, 
because  of  the  fact  that  light  darkens  silver  chloride, 
iodide,  and  bromide.  Metallic  silver  is  deposited  in 
proportion  to  the  intensity  of  the  light.  See  text 
for  description  of  process. 

Platinum  is  very  resistant  to  chemical  action  and 
for  this  reason  is  useful  in  many  chemical  processes. 
In  the  bacteriological  laboratory  the  loops  for  trans- 
ferring cultures  are  made  of  platinum  because  this 
metal  can  be  heated  to  redness  so  many  times  with- 
out deterioration.  Thermocautery  points  and  contact 
points  in  electrical  apparatus  are  made  of  platinum 
for  the  same  reason. 

Platinum  salts  (Pt.  is  tetravalent)  like  PtCl4  have 
the  property  of  stimulating  many  chemical  processes 
without  entering  into  the  final  product  (catalyzer). 
Opportunity  is  taken  here  to  introduce  the  subject  of 
colloids.  An  electrical  current  passed  between  two 
platinum  points  under  water  will  project  minute  par- 
ticles of  platinum  into  fine  (ultramicroscopic)  suspen- 
sion. Colloidal  solutions  are  not  true  solutions,  but 
stand  somewhere  between  suspension  and  solution. 
The  particles  in  colloidal  suspension  do  not  settle  out  on 
standing — and  they  cannot  be  seen  with  the  aid  of  a 


SUMMARY  OF  CHAPTER  XXIV  137 

microscope.  Colloids  do  not  pass  through  animal 
membranes  as  solutions  of  crystalloids  do.  Colloids 
are  precipitated  by  acids.  Colloidal  chemistry  is  com- 
ing into  prominence  in  the  study  of  pathological 
chemistry. 


CHAPTER  XXV. 

CARBON,  C. 

(At.  wt.  =  12.) 

WE  are  familiar  with  the  element  carbon  in  non-crys- 
talline forms  as  charcoal  and  graphite.  One  is  sur- 
prised, however,  to  learn  that  the  sparkling  diamond  is 
nothing  more  than  pure  crystallized  carbon.  The  soft, 
friable,  black  substance  seems  to  have  nothing  in 
common  with  the  white,  sparkling  stone,  the  hardest 
substance  known.  On  complete  oxidation  both  sub- 
stances yield  carbon  dioxide  and  -nothing  more.  The 
French  chemist,  Moisson,  was  able  to  produce  very 
small  diamonds  from  charcoal,  and  more  recently 
larger  diamonds  have  been  made. 

Distribution. — When  vegetable  or  animal  material  is 
heated  in  a  closed  vessel  charcoal  results,  thus  showing 
that  carbon  enters  into  the  composition  of  these  sub- 
stances in  relatively  large  amounts.  We  shall  learn 
later  that  this  element  is  the  chief  constituent  of  living 
matter.  In  combination  with  hydrogen,  oxygen  and 
nitrogen  it  is  capable  of  forming  an  enormous  variety 
of  compounds.  For  example,  the  simple  substance 
vinegar  is  composed  of  carbon,  hydrogen  and  oxygen, 
and  the  highly  complex  and  wonderful  animal  and 
vegetable  cell  substances  are  chiefly  composed  of  these 
three  elements  plus  nitrogen. 


CARBONATES  139 

The  vast  oil  and  coal  deposits  are  chiefly  carbon  and 
hydrogen.  Carbon  also  occurs  in  minerals  (carbonates) . 

Chemical  Properties. — Carbon  is  relatively  inert 
chemically  and  combines  with  other  elements  only 
under  the  influence  of  heat.  With  lime,  for  example, 
under  the  influence  of  intense  heat,  the  carbide  of 
calcium  Ca2C  is  formed.1  Heated  in  the  air  carbon  is 
oxidized  to  form  carbon  dioxide,  CO2.  This  is  the  gas 
given  off  by  animals  during  respiration  and  absorbed 
by  the  leaves  of  plants  to  be  built  up  into  complex 
vegetable  matter.  The  ultimate  product  of  oxidation 
of  the  vegetable  and  animal  matter  is  CO2.  When 
carbon  or  any  of  the  organic  compounds  are  heated  in 
an  atmosphere  poor  in  oxygen  more  or  less  of  the 
monoxide  (CO)  is  formed.  This  gas  is  deadly  to  life. 
In  the  blood  of  animals  it  unites  with  the  hemoglobin 
(red  coloring  matter)  to  form  a  stable  compound  and 
the  animal  becomes  asphyxiated.  Many  cases  of 
monoxide  poisoning  have  been  reported  as  resulting 
from  the  shutting  up  of  stoves  over  night.  Insuffi- 
cient oxygen  is  supplied  to  the  glowing  carbon  and 
carbon  monoxide  instead  of  carbon  dioxide  is  formed. 
A  "flare  back"  in  a  Bunsen  burner  brings  about  the 
same  condition  of  insufficient  oxygen  supply  and 
carbon  monoxide  is  formed. 

Carbonates. — Carbon  dioxide  in  water  solution 
forms  the  unstable  acid  H2CO3,  carbonic  acid.  In  the 
presence  of  hydroxides  of  metals  the  carbonate  is 
formed.  For  example: 

2NaOH  +  H2CO3  =  Na2CO3  +  2H2O. 
Soda  Washing 

lye.  soda. 

1  When  water  is  added  to  Ca2C  acetylene  (which  see)  is  formed.    ' 


140  CARBON 

When  only  half  the  quantity  of  the  hydroxide  is 
present,  a  hydrogen  or  acid  carbonate  is  formed. 


NaOH  +  H2CO3  =  NaHCOs  +  H2O. 
Soda  Cooking 

lye.  soda. 


The  bicarbonate  (acid  carbonate)  of  sodium  is  cook- 
ing soda  to  which  reference  has  already  been  made. 

The  carbonates  of  magnesium,  of  calcium,  of  barium 
and  of  strontium  are  insoluble,  therefore  the  addition 
of  a  soluble  carbonate  to  a  solution  of  any  salt  of  the 
above  elements  brings  about  a  precipitate.  This 
property  is  made  use  of  in  the  separation  or  estimation 
of  these  elements. 

SUMMARY  OF  CHAPTER  XXV. 

Charcoal,  graphite,  and  diamond  are  forms  of  the 
element  carbon. 

Carbon  is  found  abundantly  in  nature :  as  carbonates 
it  occurs  in  mineral  deposits,  and  the  element  enters 
into  a  large  number  of  compounds  with  H,  O  and  N  to 
form  the  chief  constituents  of  animal  and  vegetable 
matter. 

Carbon  is  relatively  inert  chemically.  It  combines, 
however,  with  various  elements  on  heating.  Carbon 
is  tetravalent.  Completely  oxidized  it  forms,  CO2, 
which  is  given  off  in  expiration.  Incomplete  oxidation 
results  in  the  formation  of  a  highly  poisonous  com- 
pound, carbon  monoxide  (CO),  which  forms  a  stable 
union  with  the  red-blood  cells. 


CHAPTER  XXVI. 
COMPOUNDS  OF  CARBON  WITH  HYDROGEN. 

THE  study  of  the  various  compounds  of  carbon  with 
hydrogen  and  with  hydrogen  and  oxygen  is  known  as 
organic  chemistry  because  the  living  cells  and  their 
products  are  such  compounds  of  carbon. 

Marsh  Gas. — The  simplest  of  the  organic  compounds 
is  the  gas  which  bubbles  up  from  the  stagnant  water 
overlying  decomposing  vegetable  matter.  If  this  gas 
be  collected  and  mixed  with  the  proper  proportion  of 
air  it  forms  an  explosive  mixture  showing  that  it  is  an 
easily  oxidizable  compound.  This  is  the  gas  which 
often  collects  in  mines  and  explodes  when  a  miner's 
lighted  torch  is  brought  in. 

By  analysis  we  learn  that  marsh  gas  is  composed  of 
four  parts  of  hydrogen  to  one  part  of  carbon.  The 
analyses  of  other  carbon  compounds  show  that  carbon 
combines  with  the  equivalent  of  four  hydrogen  atoms. 
For  example,  in  carbon  dioxide,  since  oxygen  has 
twice  the  valence  of  hydrogen,  carbon  is  said  to  have 
a  valence  of  four.  One  atom  of  carbon  will  hold  four 
atoms  of  chlorine  in  combination,  CC14.  Since  the 
valence  of  chlorine  is  one  (remember  HC1)  thus  carbon 
is  again  shown  to  be  tetravalent.  Many  other  examples 
can  be  cited. 


142     COMPOUNDS  OF  CARBON  WITH  HYDROGEN 

Marsh  gas  is  written 

H 

H— C— H 
H 

which  is  our  nearest  approach  to  the  representation  of 
our  conception  of  the  relation  of  the  atoms  to  each 
other.  In  reality  we  believe  that  the  hydrogen  atoms 
are  arranged  at  the  points  of  a  tetrahedron  with  the 
carbon  atom  as  the  centre.  When  we  increase  the 
number  of  carbon  atoms  in  a  compound  one  can  readily 
see  that  the  position  occupied  by  the  atoms  may  make 
a  considerable  difference  in  the  character  of  the  com- 
pound. A  formula  showing  the  relative  positions  of 
the  atoms  is  said  to  be  the  structural  representation, 
while  the  formula  indicating  simply  the  relative  num- 
ber of  atoms,  e.  g.,  CH4,  is  called  the  empirical  formula. 

H 

CH4  H— C— H 

Empirical  formula. 

H 
Structural  formula. 

It  will  be  seen  later  that  two  compounds  may  possess 
entirely  different  properties,  but  have  the  same  empiri- 
cal formula :  only  by  the  structural  formula  could  one 
distinguish  one  from  another  when  they  are  referred 
to. 

Methane. — Organic  chemistry  treats  of  the  various 
compounds  built  up  on  the  basis  of  marsh  gas  as  a 
unit.  The  chemical  name  of  marsh  gas  is  methane. 
A  mixture  of  methane  and  chlorine  in  diffused  day- 


CHLOROFORM  143 

light  will  react  to  form  chlorine  substitution  products 
of  methane. 

CH4        +  C12  =  HCl  +  CH3C1    mono-chlor-methane. 
CH3C1    +  Cla  =  HCl  +  CH2C12  di-chlor-methane. 
CH2C12  +  C12  =  HCl  +  CHCls    tri-chlor-methane. 
CHCla    +  C12  =  HCl  +  CCU       tetra-chlor-methane. 

Chloroform. — The  third  product  tri-chlor-methane 
is  the  compound  familiar  to  us  as  chloroform.  The 
structural  formula  is 

ci 

I 

H— C  — Cl 

Cl. 

Chloroform  is  a  heavy,  mobile  liquid,  having  a  char- 
acteristic odor  and  sweet  taste.  It  boils  at  62°  C.,  and 
the  vapors  are  not  inflammable  as  in  the  case  of  ether, 
though  when  the  vapors  are  brought  in  contact  with 
a  flame  they  are  slightly  oxidized,  forming  carbonyl 
chloride,  a  dangerous  gas.  For  this  reason  care  should 
be  exercised  in  the  use  of  chloroform  as  an  anesthetic 
near  a  lamp  or  gas  flame.  Commercially,  chloroform 
is  produced  by  the  action  of  bleaching  powder  on 
alcohol.  lodoform  is  tri-iodo-methane,  that  is,  iodine 
is  substituted  for  three  hydrogen  atoms  in  methane. 


CHCls.  CNI3.  CHBr3. 

Chloroform.  lodoform.  Bromoform. 


lodoform  is  a  yellow,  crystalline  solid,  with  a  char- 
acteristic penetrating  odor.  Its  antiseptic  properties 
are  due  to  the  slow  liberation  of  free  iodine. 


1.44    COMPOUNDS  OF  CARBON  WITH  HYDROGEN 

Methyl  Alcohol. — If  we  treat  mono-brom-methane 
with  silver  oxide  in  the  presence  of  water  we  obtain 
methyl  hydrate  and  silver  bromide. 

2CH3Br  +  Ag2O  +  H2O  =  2CH3OH  +  2AgBr. 

Methyl  hydrate  is  the  compound  which  we  obtain 
in  the  destructive  distillation  of  wood  and  call  wood 
alcohol.  Just  as  the  hydroxyl  group  OH  is  characteris- 
tic of  a  base  when  joined  to  a  metal,  it  is  when  joined 
to  an  organic  group  the  characteristic  of  an  alcohol. 
An  alcohol  then  consists  of  a  hydroxyl  group  joined  to 
an  organic  group  (radical). 

Methyl  alcohol  is  represented  structurally  by  the 
following  formula: 

H 
I 

H— C— OH 

I 
H. 

If  R  represent  any  organic  radical  then  an  alcohol 
may  be  represented  by  R.OH. 

Methyl  alcohol  is  lighter  than  water,  and  mixes 
with  it  in  all  proportions.  This  alcohol  is  used  as  a 
solvent  in  industrial  processes  and  the  fumes  often 
cause  blindness  in  the  workmen.  When  taken  inter- 
nally it  is  a  poison  and  may  cause  death.  On  account 
of  its  cheapness  there  is  a  temptation  to  use  it  as  an 
adulterant  in  the  cheaper  wines  and  whiskies  which 
is  of  course  illegal. 

Formaldehyde. — The  disinfectant  used  for  fumigat- 
ing rooms  where  patients  with  contagious  diseases  have 
been  is  formaldehyde  gas.  Formalin  is  a  40  per  cent, 
solution  of  the  gas  in  water.  An  exceedingly  small 


FORMALDEHYDE  145 

amount  is  able  to  inhibit  the  growth  of  bacteria  and 
larger  amounts  kill  them.  It  is  poisonous  for  animals 
when  taken  internally.  Strong  solutions  burn  the  skin, 
and  there  are  those  who  have  an  idiosyncrasy  for  it 
to  the  extent  that  even  very  weak  solutions  cause 
violent  skin  reactions. 
The  chemical  constitution  of  formaldehyde  is  simple  : 

its  structural  formula  is 

H 

H— 0=0. 

We  see  that  this  compound  is  methane  in  which  two 
H  atoms  are  replaced  by  O.  Observe  that  the  valence 
of  carbon  is  four  and  that  they  are  satisfied.  In 
methyl  alcohol  the  O  has  one  valence  bound  by  H,  viz.: 

H 
H— c— O— H. 


but  in  formaldehyde  both  bonds  of  the  oxygen  are 
attached  to  the  C.  Also  it  will  be  seen  that  formalde- 
hyde has  two  atoms  of  hydrogen  less.  We,  therefore, 
see  the  relation  between  methyl  alcohol  and  formalde- 
hyde. The  taking  away  of  hydrogen  means  oxidation, 
that  is,  some  oxygen  has  combined  with  these  two 
hydrogen  atoms  to  form  water  which  splits  off,  leaving 

H 


The  group 

H 

—  c=o, 

10 


146    COMPOUNDS  OF  CARBON  WITH  HYDROGEN 

(written  also  CHO)  is  called  the  aldehyde  group.  It 
is  characteristic  of  the  aldehydes  because  no  compound 
is  an  aldehyde  unless  it  possesses  such  a  group,  and 
all  compounds  possessing  this  group  are  aldehydes. 
The  aldehydes  are  made  by  oxidizing  alcohols.  In 
the  example  here  given,  methyl  alcohol  vapor  passed 
over  heated  copper  or  platinum  wire  in  the  presence 
of  air  is  oxidized  to  formaldehyde.  If  R  represent  any 
organic  group  (radical)  then  an  aldehyde  of  this 
radical  may  be  represented  by:  R.CHO. 

Organic  Acids.  —  If  formaldehyde  is  treated  with  an 
oxidizing  agent  like  potassium  permanganate  KMnO4 

it  is  oxidized  to  formic  acid  : 

H 

I 

H  O 

I  I 

H—  C=O  +  O=H—  C=O. 


Formic  acid  is  a  corrosive,  colorless  compound,  with 
a  penetrating  odor  occurring  in  the  bodies  of  ants 
(Latin  formica  =  an  ant)  .  It  also  occurs  in  the  hairs 
of  certain  caterpillars  and  in  the  stings  of  nettles. 

It  is  important  to  observe  that  only  one  hydrogen 

is  replaceable  by  the  metal  when  the  acid  is  neutralized 

by  a  base.     The  equation  for  the  reaction  of  sodium 

hydroxide  on  formic  acid  is  represented  by  the  following  : 

H  Na 

I  J 

O  O 

I  I 

H—  C=O  +  NaOH  =H—  C=O  +  H2O 

This  equation  is  usually  written 

H.COOH  +  NaOH  =  H.COONa  +  H2Q. 
Sodium 
formate. 


SUMMARY  OF  CHAPTER  XXVI  147 

Formic  acid  is  the  simplest  of  the  organic  acids. 
The  carboxyl  group 


(written  usually  COOH)  is  characteristic  of  organic 
acfds.  If  R  represent  any  organic  radical  then  an 
organic  acid  may  be  represented  by  R.COOH.  In  the 
case  of  formic  acid  R  is  only  H,  but  in  acetic  acid 
(vinegar),  for  example,  R  is  a  methyl  group,  CH3.  Now 
substituting  CH3  for  R  in  our  general  formula  for  an 
organic  acid  R.COOH,  we  have  CH3.COOH  (acetic 
acid).  The  structural  formula  of  acetic  acid  may  be 
represented  as  follows: 

H 

I 

H     O 

I       I 

H—  C—  C=O. 

H 

SUMMARY  OF  CHAPTER  XXVI. 

Organic  chemistry  deals  with  the  compounds  of 
C,  H,  O,  N.  The  natural  compounds  made  up  of  these 
elements  are  the  result  of  plant  or  animal  life  so  that 
the  term  organic  is  applied  to  all  such  compounds  to 
distinguish  them  from  the  mineral  or  inorganic  sub- 
stances. 

Marsh  gas  is  the  simplest  of  the  organic  compounds, 
and  the  nucleus  about  which  the  more  complicated 
are  arranged.  It  is  very  important  to  learn  the  various 


148     COMPOUNDS  OF  CARBON  WITH  HYDROGEN 

substitution  products  of  methane,  for  this  is  the  foun- 
dation of  organic  chemistry. 

Carbon  is  tetravalent.  The  H  atoms  of  marsh  gas 
(CH4)  are  supposed  to  be  arranged  in  space  about  the 
C  atom  as  a  centre.  A  convenient  hypothesis  is  that 
each  H  atom  is  placed  at  the  angle  of  a  tetrahedron 
(a  four-sided  solid).  It  is  conceivable  that  the  figure 
is  equilateral  if  the  four  valences  of  the  carbon  are 
satisfied  by  the  same  atoms.  Such  a  formula  the 
representation  on  paper  is  thus: 

H 

I 

H— C— H 
H 

is  called  the  structural  formula,  while  CH4  is  the  empir- 
ical formula.  Two  substances  may  have  the  same 
empirical  formula  but  different  structural  formulas. 

The  four  H  atoms  of  methane  can  be  replaced  by 
other  monovalent  atoms.  For  example,  chloroform  is 
tri-chlor-methane  (three  H  atoms  replaced  by  chlorine). 
Chloroform  is  a  colorless,  mobile  liquid.  lodoform,  a 
yellow,  crystalline  solid,  is  an  analogous  compound; 
instead  of  three  chlorine  atoms  there  are  three  iodine 
atoms  substituted  for  three  hydrogen  atoms. 

If  a  hydrogen  is  replaced  by  a  hydroxyl  group  the 
result  is  methyl  alcohol,  CH3OH. 

An  alcohol  consists  of  a  hydroxyl  group  joined  to 
an  organic  radical,  R — OH. 

If  two  hydrogen  atoms  are  replaced  by  an  oxygen 
atom  the  result  is  formaldehyde,  HCHO. 


SUMMARY  OF  CHAPTER  XXVI  149 

The  characteristic  of  the  aldehyde  group  is— CHO. 
Any  aldehyde  may  be  represented  thus:  R — CHO. 

If  two  hydrogens  are  replaced  by  an  atom  of  oxygen, 
and  one  hydrogen  replaced  by  a  hydroxyl  group  the 
result  is  an  organic  acid,  formic  acid,  H.COOH.  The 
— COOH  group  is  characteristic  of  an  organic  acid, 
R— COOH. 

An  acid  is  an  oxidized  aldehyde,  and  aldehyde  is  an 
oxidized  alcohol,  and  an  alcohol  is  an  oxidized  hydro- 
carbon. 


H 
H—  C—  H. 

H 

Methane. 

H 

1 
H—  C—  OH. 

H 

Methyl  alcohol. 

3 
H—  ( 

Formal 

I 

>=o. 

dehyde. 

OH 
H—  C=0. 

Formic  acid. 

CHAPTER  XXVI]. 
ETHERS. 

IF  methyl  (wood)  alcohol  CH3OH  is  allowed  to 
come  in  contact  with  metallic  sodium,  the  alcoholate 
of  sodium  is  formed: 

CH3OH  +  Na  =  CH3ONa. 

We  have  already  seen  that  sodium  has  a  strong  attrac- 
tion for  the  halogens  (iodine,  chlorine,  bromine  and 
fluorine),  forming  with  them  salts  or  halides.  We 
have  also  seen  that  from  methane,  CH4,  a  compound  of 
chlorine,  bromine  or  iodine  may  be  formed  CH3C1, 
CH3Br,  CH3I.  Then  if  we  put  either  of  these  three 
substances  in  solution  with  a  sodium  compound  there 
would  be  a  strong  tendency  to  form  NaCl,  NaBr 
or  Nal,  according  to  the  methyl  halide  present.  If 
CH3.O.Na  be  brought  in  contact  with  CH3I,  then  we 
would  have  Nal  formed  leaving  two  compounds  with 
unsatisfied  or  unsaturated  bonds : 
CH3.O— (or 

H 

H— C— O— ) 
'     .  I 

H 

and  CH3 —  (or 

H 

— C— H). 
H 


ETHERS  151 

The  natural  result  is  the  joining  of  these  unsaturated 

bonds  thus: 

H  H 

i  I 

H C O C H. 

I  I 

H  H 

As  a  matter  of  fact  this  actually  happens  and  we 
have  therefore  the  equation: 

CH3.O.Na  +  CH3I  =  CH3.O.CH3  +  Nal. 
Ether. 

This  compound  CH3.O.CH3,  written  also 

CH3 
CH 

is  called  an  ether  because  of  its  low  boiling-point  and 
elastic  property.  This  (methyl-methyl-ether)  is  the 
simplest  of  the  ethers.  Later  we  shall  learn  that  the 
ether  used  as  an  anesthetic  (ethyl  ether)  is  of  the 
same  type  of  compound,  namely,  two  organic  radicals 
(R)  joined  with  oxygen: 

Rs 


It  is  not  essential  that  the  two  radicals  are  the  same 
the  compound 

R 


(Ri  representing  any  other  radical,  for  example  C2H5), 
is  still  an  ether. 


152  ETHERS 

SUMMARY  OF  CHAPTER  XXVII. 

Ethers  have  the  constitution  R  —  O  —  Ri,  in  which 
R  and  Ri,  represent  any  organic  radical  as  CH3,  C2H5, 
C3H7,  etc.  It  is  not  necessary  that  the  two  organic 
groups  have  the  same  constitution. 

The  ether  given  for  anesthesia  is  ethyl  ethyl  ether, 


O  or  C2H6—  O—  C2H6. 


Ethyl  ethyl  ether  can  be  made  by  the  reaction  of 
sodium  ethyl  alcoholate  and  ethyl  iodide: 

C2H6 
C2H5.O—  Na  +  C2H6I  =  Nal  + 


In  practice  this  substance  is  produced  by  the  action 
of  sulphuric  acid  on  ethyl  alcohol.  On  distillation 
ether  comes  over. 

Ether  is  a  colorless,  mobile  liquid,  having  a  charac- 
teristic odor,  and  a  burning,  sweet  taste.  Its  specific 
gravity  is  about  0.7.  It  is  highly  inflammable.  It 
boils  at  36°  C.  Ether  for  anesthesia  contains  about 
4  per  cent,  ethyl  alcohol  and  a  small  amount  of  water. 


CHAPTER  XXV11I. 
THE  MARSH  GAS  SERIES. 

IT  has  been  shown  that  marsh  gas  CH4  in  the  presence 
of  chlorine,  iodine  or  bromine  in  the  sunlight  will 
gradually  form  methyl  chloride,  iodide  or  bromide. 
If  we  heat  one  of  these  compounds  with  sodium,  remem- 
bering the  great  affinity  sodium  has  for  the  halogens 
(Cl,  I,  Br),  we  would  expect  the  sodium  to  combine 
with  the  halogen  to  form  a  salt.  Suppose  we  take 
CH3I  as  an  example,  because  this  compound  is  more 
easily  handled  than  CH3C1  or  CH3Br,  on  account 
of  the  lower  boiling-point  of  the  former.  If  metallic 
sodium  is  brought  into  contact  with  CH3I  in  ether 
solution  (no  water  must  be  present  because  the  sodium 
would  combine  with  the  water  to  form  NaOH)  sodium 
iodide  is  formed. 

H  H 

I  I 

H C 1  +  Na  =  Nal  +  H C— . 

I  I 

H  H 

This  leaves  an  unsaturated  compound  CH3 — (that 
is,  a  carbon  atom  with  only  three  bonds  satisfied). 
According  to  chemical  laws  this  compound  readily 
combines  with  an  available  body.  What,  then,  is  the 
most  available  body  for  this  unsaturated  compound 


154  THE  MARSH  GAS  SERIES 

to  attach  itself  to?  The  molecules  of  substances  are 
so  minute  that  the  smallest  amount  we  can  appre- 
ciate must  contain  millions  of  molecules.  When  the 
reaction  takes  place  between  one  molecule  of  each, 
it  suffices  to  write  the  equation  of  single  molecules. 
In  the  reaction  we  have  millions  of  molecules  of  unsatu- 
rated  compounds  and  as  we  would  expect,  they  pair 
off,  combining  with  each  other  after  the  manner  of 
the  following: 

2CH3I  +  2Na  =  2NaI  +  CH3 CH3. 

The  structural  formula  of  CH3 — CH3  is 

H     H 

I 

H C C H. 

I         I 
H      H 

This  substance  is  called  ethane  and  is  generally  written 
C2H6.  It  is  a  gas  similar  to  methane  and  found  in 
petroleum  and  in  the  neighborhood  of  oil  wells. 
Chemically  it  reacts  like  methane.  For  example,  with 
iodine  each  of  the  H's  in  turn  are  replaceable,  forming 
ethyl  mono-,  di-,  tri-,  etc.,  iodide  (C2H5I,  C2H4I2, 
C2H3I3,  C2H2I4,  C2HI5,  C2I6).  We  come  to  know 
C2H5  as  an  organic  radical,  ethyl. 

Alcohol. — Then  if  we  treat  C2H5I  with  silver  hydrox- 
ide we  expect  to  get  an  alcohol  (see  methyl  (wood) 
alcohol),  according  to  this  equation: 

C2H6I  +  AgOH  =  Agl  +  C2H5— OH. 

This  is  ethyl  alcohol,  the  ordinary  alcohol  we  know 
in  medicine. 


SOURCE  OF  ALCOHOL  155 

Properties. — Pure  alcohol  is  a  colorless,  volatile 
liquid,  having  an  agreeable  odor  and  burning  taste. 
It  mixes  readily  with  water  and  ether  in  all  propor- 
tions. It  is  lighter  than  water,  boils  at  a  lower  tem- 
perature (78°  C.)  and  freezes  at  a  much  lower  tempera- 
ture (  —  130°  C.).  Alcohol  is  easily  oxidized:  fine 
platinum  wire  accelerates  oxidation  of  the  fumes  and 
will  thus  set  fire  to  alcohol  vapors.  It  burns  in  air 
with  a  non-luminous,  sootless  flame.  Alcohol  is  useful  on 
account  of  its  solvent  power  for  oils,  resins,  and  alkaloids. 

Source  of  Alcohol. — Yeast  is  a  unicellular  organism 
belonging  to  the  fungi.  Cultures  viewed  through  a 
microscope  are  found  to  consist  of  large  numbers  of 
single  cells.  These  cells  are  able  to  convert  certain 
sugars  into  carbon  dioxide  and  alcohol.  This  property 
is  taken  advantage  of  for  the  commercial  production 
of  alcohol.  The  simplest  example  is  the  manufacture 
of  wine  in  which  the  natural  grape  sugar  (glucose  or 
dextrose)  is  changed  by  the  yeast  to  alcohol  and  carbon 
dioxide.  The  carbon  dioxide  coming  off  as  a  gas  gives 
the  appearance  of  boiling  so  that  the  process  is  called 
fermentation  (fervere  =  to  boil).  Wine  contains  from 
10  to  20  per  cent,  alcohol.  In  the  distillation  more 
alcohol  than  water  goes  over  on  account  of  the  lower 
boiling-point  of  the  former  and  the  product  known  as 
brandy  contains  about  50  per  cent,  alcohol.  Brandy, 
of  course,  contains  higher  alcohols  (fusel  oils),  which 
give  it  the  peculiar  taste.  If  lime  is  added  and  another 
distillation  carried  out  the  product  is  almost  pure 
alcohol.  Any  vegetable  containing  starch  may  be  used 
to  manufacture  alcohol,  but  the  starch  must  first  be 


156  THE  MARSH  GAS  SERIES 

broken  down  into  sugars  before  the  yeast  can  utilize 
it.  To  accomplish  this  step  a  ferment  is  obtained 
from  sprouting  barley  and  this  (diastase)  added  to 
the  cooked  starch  in  the  process  known  as  malting. 
Malt  sugar,  grape  sugar,  and  dextrins  result.  Yeast 
is  added  and  alcoholic  fermentation  begins.  If  hops 
and  malt  are  fermented  beer  is  made.  Corn,  rye,  and 
potatoes  are  also  used,  but  here  the  mash  is  distilled 
and  whisky  is  the  result.  Beer  contains  from  5  to  8 
per  cent,  alcohol  and  whisky  contains  about  the  same 
amount  as  brajidy  (40  to  50  per  cent.). 

Fermentations  in  General. — Fermentation  is  now 
applied  generally  to  mean  the  changes  brought  about 
by  the  class  of  substances  known  as  ferments.  The 
chemical  composition  of  these  substances  is  unknown: 
they  are  products  of  living  cells  and  act  according  to 
certain  laws.  If  they  enter  into  combination  they  are 
immediately  set  free,  for  a  small  amount  of  ferment 
is  capable  of  changing  large  amounts  of  substances  if 
given  sufficient  time. 

Strictly  speaking,  fermentation  means  the  destruction 
of  sugars  with  the  production  of  carbon  dioxide  and 
alcohol  or  organic  acids,  in  contrast  to  putrefaction, 
which  is  the  decomposition  of  proteins  with  the  pro- 
duction of  ammonia  and  foul-smelling  gases.  Where 
microorganisms  are  capable  of  inducing  fermentation 
or  putrefaction,  the  former  takes  precedence  over  the 
latter.  This  means  that  in  a  decomposing  mixture, 
as  a  rule,  protein  decomposition  does  not  take  place 
and  foul  odors  do  not  arise  until  all  the  sugars  are 
destroyed  by  fermentation. 


CHLORAL  157 

Acetaldehyde.  —  We  remember  that  formaldehyde 
HCHO  was  formed  by  the  oxidation  of  methyl  alcohol, 
CH3OH,  or  the  reduction  of  formic  acid,  HCOOH. 
So  acetaldehyde  is  formed  by  the  oxidation  of  ethyl 
alcohol  C2H5OH. 

H 

I  I        II 

H  +  H2O. 


Acetaldehyde. 


Acetaldehyde  is  written  CH3CHO. 

Acetaldehyde  is  a  volatile,  colorless  liquid  with  a 
suffocating  odor.  It  is  little  used  in  medicine  but  its 
polymer,1  paraldehyde,  is  a  very  useful  and  safe 
hypnotic. 

Paraldehyde.  —  When  a  drop  of  sulphuric  acid  is 
added  to  acetaldehyde  a  condensation  occurs.  Three 
molecules  of  acetaldehyde  combine  with  one  another 
to  form  one  molecule  of  paraldehyde  (CH3CHO)3, 
a  volatile  liquid  with  a  pungent  taste  capable  of  pro- 
ducing sleep  with  very  little  depression  of  the  heart 
or  ill  after-effects.  It  should  be  kept  in  a  cool  place. 

Chloral.  —  This  well-known  hypnotic  is  a  chlorinated 
acetaldehyde. 

On  treating  acetaldehyde  with  dry  chlorine  gas  the 
following  reaction  takes  place: 

CH3CHO  +  3C12  =  CClsCHO  +  3HC1. 

Chloral  is  then  tri-chlor-acetaldehyde.  Chloral, 
itself,  is  a  colorless,  oily  liquid,  but  on  the  addition 

1  Polymer  is  a  molecule  consisting  of  two  or  more  molecules  con- 
densed into  one.  The  verb  is  polymerize. 


158  THE  MARSH  GAS  SERIES 

of  water,  crystals  of  chloral  hydrate  form,  CC13.CHO.- 
H2O.     This  is  the  compound  usually  prescribed. 

Acetic  Acid. — The  next  step  in  the  oxidation  of 
ethyl  alcohol,  after  acetaldehyde  is  formed,  is  the 
corresponding  acid  (compare  formic  acid). 

CHsCHO  +  O  =  CHsCOOH 
Acetaldehyde.  Acetic  acid. 

and  the  reverse  is  true, 

CHsCOOH  +  H2  =  CH3CHO  +  H2O 

by  the  reduction  of  acetic  acid  we  obtain  acetalde- 
hyde. 

Acetic  acid  is  the  chief  constituent  of  vinegar. 
The  usual  method  of  manufacture  is  by  growing  a 
special  fungus  or  mould  in  weak  alcohol.  When  apple 
juice  is  used  fermentation  first  takes  place,  and  the 
sugar  is  changed  to  alcohol  (hard  cider)  then  acidifica- 
tion begins.  Vinegar  contains  from  1  to  3  per  cent, 
acetic  acid.  The  slimy  sediment  sometimes  seen 
consists  of  masses  of  the  mould  which  forms  the 
vinegar  (mother  of  vinegar). 

SUMMARY  OF  CHAPTER  XXVIII. 

The  marsh  gas  series  consists  of  carbon-hydrogen 
compounds  of  gradually  increasing  complexity,  begin- 
ning with  methane  CH4  and  progressing  by  the  suc- 
cessive additions  of  CH2.  Ethane  is  CH4+CH2  or 
C2H6.  Propane  =  C2H6  +  CH2  =  C3H8,  etc. 

Ethane  may  be  formed  from  methane  by  first  pro- 
ducing the  mono  iodo  methane  CH3I  and  treating  this 


SUMMARY  OF  CHAPTER  XXVIII  159 

compound  with  metallic  sodium  in  a  water-free  medium. 
The  marsh  gas  series  may  be  built  up  in  this  manner. 

The  alcohols  may  be  formed  by  treating  the  alkyl 
iodide  with  AgOH. 

Ethyl  alcohol  C2H5OH  is  the  common  (grain) 
alcohol  of  commerce.  It  is  a  colorless,  volatile  liquid, 
lighter  than  water,  miscible  in  all  proportions  with 
water  and  ether.  The  commercial  source  is  the  fer- 
mentation of  sugars  by  yeast. 

Ferments  are  substances  of  unknown  composition 
which  are  capable  of  bringing  about  repeated  chemical 
changes  without  entering  into  the  end-products.  A 
small  amount  of  ferment  can  change  an  indefinite 
amount  of  sugar  if  given  time  enough. 

The  aldehydes  of  the  marsh  gas  series  are  made 
by  oxidizing  the  corresponding  alcohol.  Acetaldehyde 
is  the  result  of  the  partial  oxidation  of  ethyl  alcohol. 
Its  formula  is  CH3.CHO. 

Paraldehyde  is  formed  by  the  condensation  of  three 
molecules  of  acetaldehyde. 

Chloral   is   a   chlorinated   acetaldehyde;  CC13CHO. 

Acetic  acid  (vinegar)  may  be  produced  by  further 
oxidation  of  ethyl  alcohol  or  acetaldehyde.  It  is 
manufactured  by  growing  a  special  fungus  (mother  of 
vinegar)  in  weak  alcohol.  Vinegar  contains  1  to  3 
per  cent,  acetic  acid.  The  formula  for  acetic  acid 
is  CH3COOH. 

Let  the  student  compare  the  formulas  of  ethane, 
ethyl  alcohol,  acetaldehyde,  and  acetic  acid. 


CHAPTER  XXIX. 
THE  PARAFFINS. 

PETROLEUM  is  a  mixture  of  a  large  number  of  com- 
pounds composed  of  carbon  and  hydrogen.  The 
simplest  of  these  products,  methane  (marsh  gas), 
we  have  already  described.  This  has  the  composition 
CH4,  and  the  next  member  of  the  series  is  ethane  which 
we  learned  is  C2H6.  It  will  be  seen  that  the  difference 
between  these  members  is  CH2.  Ethane  was  made 
from  methane  by  first  preparing  the  iodide  CH3I 
and  treating  this  with  sodium.  By  following  this 
method  the  various  members  beginning  with  methane 
may  be  prepared: 

Methane  CH4     gas 
Ethane      C2H6     " 
Propane    CaHs     " 
Butane     C4Hio  liquid 
Pentane    C6Hi2 

and  so  on. 

The  structural  formula  for  butane  as  an  example  is: 

H 

3 H. 

H 

Observe  that  each  end  carbon  has  three  hydrogen 
atoms,  while  the  included  carbons  hold  only  two. 


THE  HIGHER  ALCOHOLS  161 

In  building  these  compounds  a  methyl  group,  CH3, 
is  added,  but  it  will  be  remembered  that  one  of  the 
end  hydrogens  is  split  off  to  make  room  for  the  attach- 
ment of  the  carbon  atom.  This  explains  why  the  differ- 
ence between  successive  members  is  CH2  rather  than 
CH3. 

As  we  proceed  upward  in  this  series  the  compounds 
become  less  volatile,  that  is,  their  boiling-point  in- 
creases. These  compounds  have  been  isolated  from 
natural  petroleum,  but  it  is  a  less  difficult  task  to  build 
them  from  methane  and  ethane  than  to  attempt 
to  separate  them.  Gasoline  is  a  mixture  of  several 
members  of  this  series. 

Derivatives  of  the  Hydrocarbons. — Since  methane  and 
ethane  furnished  us  on  oxidation  the  corresponding 
alcohols  (methyl  and  ethyl)  it  is  possible  to  prepare 
the  alcohols  of  the  other  members  of  this  series.  Hence 
we  have  propyl  alcohol,  butyl  alcohol,  and  so  on.  We 
also  have  the  corresponding  aldehydes,  ethers,  and 
acids. 

The  Higher  Alcohols. — Ethane  we  have  seen  is 
C2H6  and  ethyl  alcohol  is  C2H5OH.  Then  if  propane 
is  C3H8,  propyl  alcohol  is  CsHrOH  and  its  structural 
formula  is: 


H. 

H 

This  we  call  a  primary  alcohol,  but  if  the  hydroxyl 
group,  which  we  remember  is  the  characteristic  group 
11 


162  THE  PARAFFINS 

of  an  aclohol,  is  attached  to  the  middle  C  as  in  the 
following : 


we  name  it  a  secondary  alcohol.  We  shall  find  little 
need  of  distinguishing  between  primary  and  secondary 
alcohols,  but  we  shall  find  it  to  our  advantage  to  pay 
close  attention  to  the  following  compound: 

OH  OH  OH 

I       I       I 

H C C C H. 

I         I         I 
H      H      H 

Observe  that  there  are  three  alcohol  groups  here, 
and  we  call  it  a  tri-hydroxy  alcohol  or  tri-atomic  alcohol. 
This  is  the  mon-atomic  alcohol  already  described  with 
the  further  replacement  of  two  hydrogen  atoms  by 
hydroxyl  groups.  If  there  were  two  hydroxyl  groups 
it  would  be  called  a  di-atomic  alcohol. 

Glycerine. — The  tri-atomic  alcohol,  whose  formula 
has  just  been  stated,  is  the  substance  known  in  medicine 
as  glycerine. 

Properties. — Glycerine  is  so  named  on  account  of 
its  sweet  taste.  As  we  ordinarily  know  it,  this  tri- 
hydroxy  alcohol  is  an  odorless,  clear,  thick  liquid, 
although  in  its  pure  state  it  is  crystalline.  It  has  the 
property  of  absorbing  water  (hygroscopic),  and  on 
this  account  a  thin  film  will  keep  surfaces  moist.  It 
is  useful  as  a  vehicle  in  pharmacy. 

Glycerine  is  made  from  fats  by  treating  them  with 


SUMMARY  OF  CHAPTER  XXIX  163 

superheated  steam,  and  it  is  a  by-product  in  the 
manufacture  of  soap.  The  reactions  will  be  discussed 
under  fats. 

SUMMARY  OF  CHAPTER  XXIX. 

The  paraffin  series  consists  of  saturated  hydrocarbons 
of  the  marsh  gas  series.  Various  members  of  the  series 
are  found  in  petroleum.  The  simplest  member  is 
methane,  CH4.  Ethane  is  C2H6.  By  the  addition  of  a 
CH2  group  to  any  member  the  next  higher  is  obtained. 
The  first  four  members  are  gases — the  remainder  are 
liquids  (excepting  the  most  complex  members  which 
are  solid  at  ordinary  temperature) . 

The  structural  formulas  of  these  compounds  are 
very  important.  The  empirical  formulas  tell  only  a 
very  small  part  of  the  story  of  their  composition. 

Derivatives  of  these  hydrocarbons  are  known. 
These  correspond  to  the  various  compounds  of  methane 
formed  by  replacing  the  H  atoms  with  other  elements 
or  groups.  It  will  be  seen  that  more  derivatives  of 
the  same  kind  are  obviously  possible;  for  example, 
while  in  the  case  of  methane  only  one  alcohol  was 
possible,  in  propane  three  are  possible.  Likewise 
more  chlorine  derivatives  are  possible  in  the  higher 
members  of  the  series. 

In  a  primary  alcohol  the  hydroxyl  group  is  attached 
to  the  end  carbon;  in  a  secondary  alcohol  this  group 
is  attached  to  the  second  carbon,  etc. 

A  monatomic  alcohol  possesses  one  hydroxyl  group: 
a  diatomic  alcohol,  two  groups,  etc. 


164  THE  PARAFFINS 

Glycerine  is  a  common  example  of  a  tri-atomic 
alcohol.  It  has  the  composition  (CH2)2 '  CH  *  (OH)3. 

CH2OH 
CHOH 

I 

CHsOH. 

It  is  so  named  on  account  of  its  sweet  taste.  It 
is  a  thick,  clear  syrup,  miscible  in  water  in  all  pro- 
portions and  crystallizable  in  the  absolutely  pure 
state.  Glycerine  is  a  by-product  of  soap  manufacture. 


CHAPTER  XXX. 
SUGARS. 

THE  compound  C6Hi4  is  one  of  the  paraffins,  that  is, 
it  is  composed  of  six  methyl  groups  connected  to  form 
a  chain  in  the  following  manner: 


— H. 
H      H      H      H 

Obviously  several  alcohol  derivatives  of  this  com- 
pound are  possible.  If  one  of  the  end  H's  were  re- 
placed by  OH  the  compound  would  be  hexyl  alcohol, 
C6Hi3OH.  The  other  extreme,  or  complete  hydroxy- 
lation,  would  of  course  consist  'of  one  OH  group  for 
every  C  atom.  There  could  not  be  any  more  because 
if  more  than  one  OH  group  attaches  itself  to  a  C  atom 
two  of  them  combine  and  are  split  off  as  water  (H2O). 

The  compound  resulting  from  the  replacement  of 
one  of  the  H's  on  each  C  atom  then  is  hexatomic 
alcohol : 

OH      H      H    OH  OH  OH 

H— C— C— C— C— C— C— H 
C—C— C— C— C       C 

H     OH  OH     H      H      H 

(Notice  that  the  hydroxyl  groups  are  not  all  on 
same  side.) 


166  SUGARS 

This  compound  is  found  in  nature  and  is  called 
mannite.  It  is  a  white  crystalline  substance  with  a 
sweet  taste.  It  is  fermentable  and  in  other  ways  it  is 
similar  to  sugars. 

Mannite  is  used  extensively  in  bacteriology  to 
differentiate  certain  kinds  of  bacilli,  especially  the 
organisms  causing  bacillary  dysentery.  Just  one  step, 
one  slight  chemical  change,  brings  us  to  mannose, 
which  is  a  sugar.  By  oxidizing  one  of  the  end  groups 
we  obtain  an  aldehyde.  (Remember  that  formal- 
dehyde was  produced  by  oxidizing  methyl  alcohol.) 
Mannose  is  a  hexatomic  alcohol  (mannite)  with  an 

aldehyde 

H 

-c/o,  :  & 

group  on  the  end: 

OH     H      H     OH  OH  H 

_J_J         '_'_'_   / 

-c— c— c— c— c- 

H     OH  OH     H      H 

If  now  we  change  the  relative  positions  of  the  H 
and  OH  groups,  we  have  the  formula: 

OH    H      H     OH     H  H 

I    I     I     I     I      / 

TT  f^  f~^  C^  (~*  ^"1  C^ C\ 

I     !      I      !      I 

H     OH   OH    H     OH 

This  is  grape  sugar  (glucose). 

Properties  of  Grape  Sugar. — Grape  sugar  is  commonly 
known  as  glucose.  (Glyc  or  glue  stem  in  a  word  indi- 
cates sweetness,  and  the  suffix  ose  shows  that  the  sub- 


THE  POLARISCOPE  167 

stance  is  a  sugar  in  the  chemical  sense.)  Glucose  is  a 
white  crystalline  substance,  soluble  in  water  and 
slightly  soluble  in  alcohol.  It  possesses  a  pleasant, 
sweet  taste,  but  no  odor.  Glucose  occurs  in  nature 
in  combinations  known  as  glucosides.  It  occurs  in 
grapes  uncombined,  hence  the  name  grape  sugar. 
Commercially  it  is  obtained  by  boiling  starch  with 
dilute  acid  (sulphuric  acid  is  generally  used  because 
it  can  be  so  easily  eliminated  afterward).  The  reason 
why  glucose  can  be  obtained  from  starch  in  this  manner 
will  appear  later. 

The  Polariscope. — A  ray  of  light  is  said  to  be  a 
vibration  in  ether.  If  we  liken  it  to  the  vibration  of 
a  harp  string  we  find  that  the  excursions  are  not  all 
in  the  same  place.  In  other  words,  if  the  string  were 
stretched  in  the  direction  exactly  perpendicular  to  the 
earth  the  vibrations  when  the  string  is  struck  would 
not  be  confined  to  excursions  north  and  south  or  east 
and  west,  but  would  swing  to  any  or  all  points  of  the 
compass.  Such  is  our  conception  of  the  vibrations 
of  a  ray  of  light.  It  is  possible  to  keep  the  vibrations 
in  the  same  plane:  suppose  two  plane  boards  were 
placed  one  on  each  side  of  the  string  in  such  a  manner 
that  the  string  could  move  to  and  fro  in  one  direction. 
The  string  would  vibrate  then  in  one  plane.  The 
same  thing  can  be  accomplished  with  light  by  allowing 
the  ray  to  pass  through  a  prism.  The  light  waves 
vibrate  in  one  plane  just  as  the  string  did  and  the 
result  is  polarized  light.  If  a  ray  of  polarized  light 
is  passed  through  solutions  of  sugars,  the  vibration 
plane  is  turned  to  the  right  or  left.  Suppose  the 


168  SUGARS 

plane  of  vibration  of  a  particular  beam  of  polarized 
light  is  exactly  vertical.  The  beam  is  passed  through 
a  solution  of  glucose.  Now  the  plane  of  vibration  is 
not  vertical  but  has  been  rotated  to  the  right  (clock- 
wise) so  many  degrees.  Glucose  then  is  said  to  be 
dextro-rotary  (dextra  =  right) .  The  amount  of  rotation 
is  proportionate  to  the  amount  of  sugar  present.  It 
is  therefore  possible  to  determine  how  much  glucose  is 
present  in  a  solution  without  going  through  the  process 
of  recrystallizing  it  several  times  to  purify  it  and 
finally  drying  and  weighing  it.  The  instrument  with 
which  one  measures  the  rotation  of  the  plane  of  light 
is  called  a  polariscope.  The  number  of  degrees  a  prism 
must  be  rotated  to  bring  the  plane  back  to  the  original 
position  is  read  and  from  this  the  amount  of  sugar  can 
be  calculated.  The  polariscope  is  used  extensively  in 
the  sugar  industries  and  in  analyses  of  sugar-contain- 
ing substances.  It  is  essential  in  accurate  analysis  of 
urines  which  contain  sugar. 

The  Asymmetric  Carbon  Atom. — The  power  to  rotate 
the  plane  of  polarized  light  is  due  to  the  presence  of 
a  carbon  atom  which  has  all  four  of  its  bonds  satisfied 
by  different  kinds  of  groups.  Such  a  carbon  atom  is 
said  to  be  asymmetric.  If  any  two  of  these  groups  are 
the  same,  the  carbon  atom  is  not  asymmetric.1 

Suppose,  for  example,  that  we  substitute  for  three 
of  the  hydrogen  atoms  in  methane  the  following 
groups  (CHs),  (OH),  and  (COOH),  i.  e.,  a  methyl,  a 
hydroxyl,  and  a  carboxyl  group.  kOne  H  atom  remains. 

1  Asymmetric  means  without,  symmetry  (not  symmetrical). 


REDUCING  POWER  OF  SUGARS  169 

We  have  now  a  compound  containing  an  asymmetric 
carbon  atom,  and  according  to  the  above  statement 
should  rotate  the  plane  of  polarized  light. 

This  compound 

H 

(OH)— C— COOH 
(CH3) 

is  lactic  acid.  It  rotates  the  plane  of  polarized  light 
to  the  right.  Should  we  change  the  relative  positions 
of  the  methyl  and  carboxyl  groups  we  still  have  lactic 
acid,  but  this  lactic  acid  rotates  the  plane  to  the  left. 
This  is  the  basis  upon  which  our  theories  of  optical 
activity  of  chemicals  is  built. 

Reducing  Power  of  Sugars. — Returning  to  the  graphic 
formula  of  dextrose  we  find  that  it  contains  an  aldehyde 

group, 

H 

I 


We  remember  that  one  of  the  chief  characteristics  of 
an  aldehyde  is  its  power  to  reduce  substances,  that  is, 
take  oxygen  from  other  substances  and  become  oxidized 
itself.  To  form  an  acid;  the 

/^ 
— Cf  group  becomes       O 

XH  || 

— C  —OH. 

We  therefore  suspect  dextrose  of  being  able  to  reduce 
substances.  Testing  the  substance  for  this  property 
we  find  that  it  is  so.  If  an  alkaline  solution  of  a  copper 


170  SUGARS 

salt  be  boiled  in  the  presence  of  dextrose  the  copper  is 
reduced  and  settles  out  as  a  bright  red,  fine  precipitate 
(copper  oxide,  Cu2O). 

The  solution  best  adapted  for  applying  this  fact  in 
testing  for  dextrose  is  composed  of  copper  tartrate 
and  sodium  hydroxide.  This  solution  is  usually  known 
as  Fehling's  solution. 

Levulose. — Another  sugar,  which  on  analysis  would 
yield  carbon,  hydrogen  and  oxygen  in  exactly  the  same 
proportions  as  found  in  dextrose,  rotates  the  plane 
of  light  to  the  left  (contra  clock-wise)  and  is,  there- 
fore, called  levulose.  It  is  the  sugar  found  in  honey 
and  also  in  fruits.  The  graphic  formula  of  levulose 
differs  from  that  of  dextrose  in  that  the  CHO 
group  is  not  at  the  end  of  the  chain  but  inside. 
It  is  therefore  not  an  aldehyde  strictly  but  a  ketone 
on  account  of  the  relative  position  of  the  aldehyde 
group.  The  strictly  aldehyde  sugars  are  called  aldoses 
and  ketone  sugars  named  ketoses.  Levulose  reduces 
Fehling's  solution  like  dextrose  and  can  be  fermented 
(i.  e.,  broken  up  by  ferments  to  form  acids  and  carbon 
dioxide),  though  less  readily  than  dextrose. 

Monosaccharids. — Dextrose  and  levulose  are  typical 
examples  of  the  several  simple  hexoses  or  monosac- 
charids.  The  group  which  they  represent  are  called 
monosaccharids  to  distinguish  them  from  the  group, 
the  members  of  which  are  formed  by  the  chemical 
union  of  two  simple  sugars. 


SUMMARY  OF  CHAPTER  XXX  171 

SUMMAKY   OF   CHAPTER   XXX. 

Hexane  has  the  formula  C6Hi4.  It  is  possible  to 
replace  six  H  atoms  with  hydroxyl  groups.  No  more 
OH  groups  can  be  joined  to  this  compound  because 
if  more  than  one  such  group  is  attached  to  the  same 
carbon  atom,  water  would  be  split  off  by  the  union  of 
the  two. 

One  hexa-hydroxy-hexane  found  in  nature  is  man- 
nite.  This  alcohol  is  very  similar  in  its  physical  proper- 
ties to  sugars.  It  is  used  in  bacteriological  work. 

If  one  of  the  end  alcohol  groups  of  mannite  be  oxi- 
dized to  an  aldehyde  group,  the  result  is  mannose, 
a  sugar. 

By  shifting  the  relative  positions  of  the  middle  H 
and  OH  groups  in  mannose,  grape  sugar,  another 
sugar  is  obtained.  Glucose  is  a  white  crystalline 
substance,  soluble  in  water  and  slightly  soluble  in 
alcohol,  with  a  sweet  agreeable  taste  and  without 
odor.  It  is  found  in  grapes  and  other  fruits.  It  can 
be  obtained  by  hydrolyzing  starch. 

The  polariscope  is  an  instrument  by  means  of  which 
the  rotation  of  the  plane  of  polarized  light  is  determined. 
In  passing  through  sugar  solutions  the  plane  of  polar- 
ized light  is  rotated  to  the  right  or  left,  and  the  amount 
of  rotation  is  directly  proportional  to  the  amount  of 
sugar  present.  This  is  a  simple  means  for  the  deter- 
mination of  sugars  in  solution.  The  power  to  rotate 
the  plane  of  light  depends  upon  the  presence  of  an 
asymmetric  carbon  atom  in  the  compound. 

On  account  of  the  presence  of  an  aldehyde  group 


172  SUGARS 

in  the  hexoses  (six  carbon  sugars),  these  compounds 
are  capable  of  reducing  substances  like  copper  tartrate 
in  alkaline  solution.  Both  aldoses  and  ketoses  (which 
see)  have  reducing  power.  The  copper  solution  in 
alkaline  tartrate  used  for  testing  sugars  is  commonly 
known  as  Fehling's  solution. 

Levulose  is  fruit  sugar.  Solutions  of  this  sugar 
rotate  the  plane  of  polarized  light  to  the  left  or  in 
opposite  direction  the  rotation  by  grape  sugar  (dex- 
trose). Levulose  is  a  ketose.  It  is  found  in  honey. 

Dextrose  and  levulose  are  examples  of  simple  sugars 
(hexoses)  and  are  classed  as  monosaccharids  in  order 
to  distinguish  them  from  the  di-  and  polysaccharids 
formed  by  the  union  of  two  or  more  monosaccharids. 

There  are  also  sugars  containing  only  five  carbon 
atoms  termed  pentoses.  They  are  sometimes  found 
in  human  urine  but  are  of  more  interest  to  the  physio- 
logical chemist. 


CHAPTER  XXXI. 
POLYSACCHARIDS. 

Cane  Sugar. — The  familiar  crystalline  substance 
used  extensively  for  sweetening  is  a  result  of  chemical 
union  between  the  two  monosaccharids  already  de- 
scribed. Dextrose  and  levulose  combined  with  the 
loss  of  one  molecule  of  water,  form  cane  sugar  or 
saccharose.  Both  dextrose  and  levulose  have  the 
empirical  formula  CeHi2O6.  Combination  of  these 
two  produces  Ci2H24Oi2,  but  there  is  lost  in  the  process 
of  uniting  one  molecule  of  water  H2O,  therefore  we 
have  as  the  empirical  formula  of  saccharose  Ci2H22On. 

Properties  of  Cane  Sugar. — Cane  sugar  is  found  in 
the  juice  of  sugar  cane,  in  beets,  in  bananas  and  other 
fruits.  It  crystallizes  easily  from  concentrated  solutions, 
and  is  therefore  easily  obtained  in  a  pure  state.  Solu- 
tions of  cane  sugar  rotate  the  plane  of  polarized  light 
to  the  right.  Fehling's  solution  is  not  reduced,  show- 
ing that  the  aldehyde  groups  of  the  simple  sugars 
composing  it  are  completely  masked. 

What  evidence  is  there  that  cane  sugar  is  composed 
of  dextrose  and  levulose?  Boil  some  cane  sugar 
with  weak  hydrochloric  acid  (1  part  concentrated 
HC1  to  100  c.c.  solution  of  cane  sugar)  for  two  hours. 
The  hydrochloric  acid  may  be  removed  by  precipitating 


I 

174  POLYSACCHARIDS 

with  lead  or  silver  salts.  Filtering  through  charcoal 
gives  us  a  clear,  colorless  solution,  which  we  may  now 
compare  with  part  of  the  original  solution  (cane  sugar 
solution).  The  original  solution  rotated,  the  polar- 
ized light  to  the  right,  now  the  solution  is  levorotary 
(rotating  to  the  left).  The  original  solution  did  not 
reduce  Fehling's  solution  but  the  new  clear  liquid  does 
so  very  vigorously.  From  the  original  solution  only 
one  substance  could  be  crystallized,  from  the  recent 
liquid  two  substances  can  be  separated,  the  one  dex- 
trorotary  the  other  levorotary.  Further  chemical 
test  show  these  substances  to  be  dextrose  and  levulose. 
It  is  thus  proved  that  hydrochloric  acid  adds  the  lost 
molecule  of  water  and  splits  cane  sugar  into  its  simple 
sugars.  The  word  hydrolysis  has  been  proposed  to 
describe  this  process  (hydro  =  water;  lysis  =  breaking 
down).  Thus  this  word  is  applied  to  all  processes 
which  add  water  chemically  to  a  substance  and  divide 
it  into  its  component  parts. 

Invertase. — We  found  that  boiling  with  hydrochloric 
acid  changed  the  power  of  the  solution  to  rotate  the 
plane  of  light,  that  is,  it  reversed  the  direction  of 
rotation  to  almost  an  equal  extent  in  the  other  di- 
rection. It  practically  inverted  the  rotation — so  we 
speak  of  the  products  of  hydrolysis  as  invert  sugar, 
and  of  the  process  as  an  inversion.  Living  yeast 
cells  or  extracts  of  yeast  cells  are  also  capable  of 
bringing  about  the  inversion  of  cane  sugar,  acting  at 
the  temperature  of  the  human  body.  The  substance 
in  the  yeast  which  acts  in  this  manner  is  capable  of 
converting  many  times  its  own  weight  of  cane  sugar, 


I 
OTHER  DISACCHARIDS  175 

it  obeys  certain  laws  of  rate  of  reaction,  and  it  is  killed 
by  heat.  A  substance  answering  such  a  description  is 
known  ,as  a  ferment.  Names  of  ferments  of  this  class 
end  in  ase,  and  the  stem  of  the  word  indicates  either 
their  action  or  the  substance  they  change.  The 
logical  name  for  the  inverting  ferment  is  invertase. 
Invertases  occur  in  the  intestinal  juices  having  been 
secreted  by  the  mucous  lining  of  the  intestine.  It 
is  by  means  of  these  ferments  that  the  higher  sugars 
(disaccharids)  are  reduced  to  simple  sugars  for  absorp- 
tion in  the  process  of  digestion.  Invertases  are  found 
in  small  amounts  in  the  blood. 

OTHER  DISACCHARIDS. 

Milk  Sugar. — If  some  copper  sulphate  is  added  to 
skim  milk  and  then  a  small  amount  of  sodium  hydrox- 
ide, all  the  white  substance  of  the  milk  will  be  co- 
agulated. Should  we  filter  the  mixture  we  obtain  a 
clear  liquid  from  which  on  evaporation  a  white,  sweet 
substance  crystallizes.  This  is  milk  sugar.  The 
Latin  word  for  milk  is  lactis,  the  ending  -ose  indicates 
a  sugar;  milk  sugar  is  therefore  well  named  lactose. 

Solutions  of  lactose  rotate  the  plane  of  polarized 
light  to  the  right,  and  also  reduce  Fehling's  solution. 
Lactose  is  sweet,  but  not  so  sweet  as  glucose  (dextrose), 
and  it  is  not  so  soluble  in  water  as  the  latter,  nor  is 
it  so  easily  fermentable. 

Boiling  with  acid  (hydrolysis)  breaks  up  lactose 
into  dextrose  and  another  simple  sugar,  galactose. 
The  mucous  lining  of  the  intestines  yields  a  ferment 
known  as  lactase,  capable  of  hydrolyzing  lactose. 


176  POLYSACCHARIDS 

In  the  digestion  of  lactose,  this  lactase  hydrolyzes 
it  before  it  is  absorbed  by  the  villi  of  the  intestinal 
wall. 

Lactose  is  unique  in  being  the  only  disaccharid  of 
animal  origin.  It  is  found  in  the  milk  of  all  mammals : 
about  5  per  cent,  of  cow's  milk  and  about  7  per  cent, 
of  human  milk  is  lactose.  From  whatever  source 
it  is  obtained  it  is  the  same  chemically. 

Malt  Sugar. — Malt  sugar  is  a  disaccharid  composed 
of  two  molecules  of  dextrose,  yielding  these  on  hydro- 
lysis by  boiling  with  an  acid  or  under  the  influence  of 
maltase.  Maltose  is  sweet,  is  dextrorotary,  and  reduces 
Fehling's  solution.  It  is  found  in  malt  where  it  is 
produced  from  starch  by  the  action  of  a  ferment 
derived  from  germinating  (sprouting)  grain. 

STARCHES. 

The  reserve  material  of  plants  is  stored  in  the 
form  of  pure  white  insoluble  substances  called  starches. 
Most  of  the  dry  material  of  the  potato,  for  example, 
is  starch;  corn  also  contains  a  high  percentage  of 
this  carbohydrate.  A  prominent  characteristic  of 
starch  is  its  reaction  with  iodine  to  form  a  blue  color, 
which  disappears  on  heating  but  reappears  on  cooling. 
To  test  any  mixture  for  the  presence  of  either  of  these 
substances  (starch  or  iodine)  one  has  merely  to  add 
the  other. 

Under  the  microscope  starch  is  found  to  be  com- 
posed of  small,  oval  grains,  having  on  them  lines 
forming  elongated  ellipses  drawn  about  a  common 
centre.  Starches  from  different  sources  have  different 


SUMMARY  OF  CHAPTER  XXXI  177 

shapes  and  markings,  but  so  far  as  is  known  they  are 
the  same  chemically.  In  fact  the  exact  composition, 
of  starch  is  not  known.  •  It  is  evident  from  many  studies 
that  it  is  composed  of  a  group  of  molecules  of  dextrose, 
but  how  many  and  their  manner  of  combination  has 
not  been  determined.  Boiling  with  mineral  acids 
decomposes  starch  with  the  formation  of  dextrose 
(glucose)  and  dextrins.  A  ferment,  amylase  (amylum 
=  starch),  found  in  the  saliva,  in  pancreatic  juice  and  in 
sprouting  grain  is  also  capable  of  hydrolyzing  starch 
in  the  same  manner. 

The  starch  grains  have  an  outer  coat  of  cellulose 
(wood  tissue)  which  protects  it  from  ferment  action 
until  it  .is  broken.  Heat  ruptures  this  coat  so  that 
cooking  prepares  the  starch  for  digestion.  In  this 
we  find  the  reason  for  the  indigestibility  of  raw  starch, 
except  by  cows  and  goats,  whose  intestinal  juices 
contain  ferments  capable  of  dissolving  cellulose. 

Starch  is  the  great  source  of  commercial  glucose. 
Grain  alcohol  is  made  by  hydrolysis  and  fermentation 
of  starches.  (See  Ethyl  Alcohol.) 

Cellulose. — Cellulose  is  a  complex  compound  of 
sugars  and  starches  in  chemical  combination.  It  is 
characterized  by  its  extreme  insolubility.  Wood  fibre 
is  largely  cellulose. 

SUMMARY  OF  CHAPTER  XXXI. 

Polysaccharids  are  carbohydrates  made  up  of  two 
or  more  monosaccharids.      Disaccharids  are  polysac- 
charids  consisting  of  two  monosaccharids, 
12 


178  POLYSACCHARIDS 

Cane  sugar  is  a  disaccharid  composed  of  dextrose 
and  levulose;  that  is,  1  molecule  of  cane  sugar  is 
composed  of  1  molecule  of  dextrose,  plus  1  molecule 
levulose,  minus  1  molecule  water.  Dextrose  (C6Hi2O6) 
+  levulose  (C<Hi^O0)  =  C^H^O^,  but  one  molecule 
H2O  is  lost,  so  the  empirical  formula  of  cane  sugar  is 


Cane  sugar  is  also  called  saccharose  (sweet  sugar) 
or  sucrose. 

Cane  sugar  does  not  reduce  Fehling's  solution. 
We  know  that  dextrose  which  is  included  in  cane 
sugar  reduces  Fehling's  (evidence  of  an  aldehyde 
group).  We  therefore  conclude  that  the  aldehyde 
group  in  cane  sugar  is  masked. 

Boiling  with  acids  adds  a  molecule  of  water  to  cane 
sugar  and  splits  it  into  dextrose  and  levulose. 

Invertase  is  a  ferment  found  in  yeast  which  is  capable 
of  hydrolyzing  cane  sugar  into  the  same  products 
as  acids  do. 

Milk  sugar  (lactose)  is  a  disaccharid  occurring  in 
milk.  It  is  composed  of  two  monosaccharids  :  dextrose 
and  galactose.  Lactose  is  the  animal  sugar  —  it  has 
not  been  found  in  plants.  It  is  dextrorotary. 
Lactase  is  the  ferment  which  hydrolyzes  lactose. 
Lactose  reduces  Fehling's  solution. 

Maltose  is  malt  sugar,  composed  of  two  molecules 
of  dextrose.  It  is  dextrorotary  and  reduces  Fehling's 
solution.  Maltase  is  the  ferment  which  hydrolyzes 
malt  sugar. 

Starches  are  the  reserve  materials  of  plants.  They 
are  composed  of  an  unknown  number  of  molecules  of 


SUMMARY  OF  CHAPTER  XXXI  179 

dextrose.  Starch  grains  from  different  sources  have 
different  sized  grains  and  diverse  markings  on  them. 

Starch  grains  have  an  outer  covering  of  cellulose 
(wood  fibre) ;  until  this  covering  is  broken  starch  grains 
are  not  soluble  in  water.  Boiling  ruptures  the  capsule 
and  a  part  of  the  contents  is  soluble  in  water.  Boiling 
with  dilute  acids  hydrolyzes  starch  into  dextrose  and 
dextrins.  Diastase,  a  ferment  found  in  the  saliva,  and 
amylase,  a  ferment  found  in  the  intestine,  also  hydro- 
lyze  starch. 

Starch  reacts  characteristically  with  iodine  to  form 
a  blue  color. 

Inulin  is  similar  to  starch,  but  it  is  a  polysaccharid 
composed  of  an  unknown  number  of  molecules  of 
levulose. 

Cellulose  is  also  a  polysaccharid,  characterized 
by  its  extreme  insolubility.  Wood  fibre  is  chiefly 
cellulose.  • 


CHAPTER  XXXII. 
THE  DIGESTION  OF  CARBOHYDRATES. 

CARBOHYDRATE  is  a  comprehensive  term,  including 
simple  and  complex  sugars  and  starches.  Generally 
speaking,  the  carbohydrates  are  so  named  because 
they  contain  carbon  in  combination  with  hydrogen 
and  oxygen,  the  latter  two  in  the  same  ratio  as  they 
occur  in  water  (2H  to  1O). 

In  the  Mouth. — Starches  are  the  only  carbohydrates 
which  undergo  chemical  change  in  the  mouth.  Cooked 
starches  are  hydrolyzed  by  the  amylase  (diastase) 
in  the  saliva  to  dextrose  and  dextrins.  Raw  starch 
is  indigestible.  The  action  of  the  saliva  is  stopped  as 
soon  as  the  food  comes  into  contact  with  the  hydro- 
chloric acid  of  the  stomach,  for  the  starch  splitting 
ferment  is  active  only  in  alkaline  medium. 

In  the  Stomach. — Practically  no  carbohydrate  diges- 
tion takes  place  in  the  stomach.  The  food  entering 
the  stomach  is  already  mixed  with  saliva  which  con- 
tinues to  act  until  the  acid  of  the  stomach  stops  it. 
There  is  no  absorption  of  carbohydrates  from  the 
stomach. 

In  the  Intestines. — As  soon  as  the  food  reaches  the 
small  intestine  the  reaction  is  again  changed  to  alkaline. 
The  intestinal  juices  coming  from  the  pancreas  and 
from  the  wall  of  the  intestine  contain  ferments  which 


STORAGE  OF  CARBOHYDRATES  181 

split  starches  and  disaccharids.  All  carbohydrates 
capable  of  digestion  are  reduced  to  monosaccharids 
before  being  absorbed;  for  example,  starches  and 
maltose  are  reduced  to  dextrose;  saccharose  (cane 
sugar)  to  dextrose  and  levulose,  and  lactose  (milk 
sugar)  to  dextrose  and  galactose.  Dextrose  (grape 
sugar),  levulose  (fruit  sugar),  and  galactose  (from 
milk  sugar)  are  absorbed  as  such  without  change. 

Fate  of  the  Sugars. — Some  of  the  sugars  are  destroyed 
by  fermenting  bacteria  in  the  intestine  before  they 
can  be  absorbed.  Most  of  them  are  absorbed  and 
either  stored  in  the  body  as  glycogen  or  fat  or  oxidized 
to  form  heat.  On  oxidation  they  yield  C02  and  H20. 
If  too  large  amounts  are  absorbed,  the  part  which  the 
body  cannot  care  for  is  excreted  in  the  urine. 

Energy  Furnished  by  Carbohydrates. — The  body  is 
capable  of  oxidizing  carbohydrates  to  their  ultimate 
products  (CO2  and  H20),  therefore  they  furnish  as 
much  heat  to  the  body  as  they  would  in  bomb  calori- 
metric  combustion.  While  the  various  sugars  differ 
slightly  in  the  number  of  Calories  per  gram  they  yield, 
the  average  for  a  normal  diet  is  4  Calories  per  gram. 

Storage  of  Carbohydrates. — When  the  body  requires 
less  carbohydrates  than  is  assimilated  the  excess  of 
simple  sugars  is  used  to  build  up  a  compound  corre- 
sponding to  vegetable  starch.  This  substance  of  un- 
known composition,  called  glycogen,  is  formed  in  the 
liver  and  stored  there  or  in  muscles  until  it  is  needed. 
When  dextrose  is  needed  the  glycogen  is  broken  down 
to  yield  it.  Glycogen  gives  a  red  color  with  iodine 
instead  of  the  blue  as  in  the  case  of  starch. 


182       THE  DIGESTION  OF  CARBOHYDRATES 

Sugars  may  also  be  converted  into  fats  in  the  body 
and  stored  as  such. 

The  average  normal  dietary  for  a  150  pound  man, 
at  moderate  work,  contains  about  500  grams  (dried)  of 
mixed  carbohydrates  per  day. 

SUMMARY  OF  CHAPTER  XXXII. 

The  digestion  of  carbohydrates  which  takes  place — 

In  the  mouth:  Starches  hydrolyzed  by  amylase  to 
dextrins  and  dextrose. 

In  the  stomach:  No  carbohydrate  digestion  after 
the  contents  become  acid.  No  absorption. 

In  the  intestines:  Fresh  amylase  from  pancreas  and 
wall  of  intestine  continue  hydrolysis.  All  digestible 
polysaccharids  reduced  to  monosaccharid,  and  absorbed 
as  such. 

Fate  of  absorbed  monosaccharids :  (1)  either  oxidized 
to  give  heat  to  body,  or  (2)  changed  into  glycogen 
(animal  starch)  and  stored  in  liver  and  muscles,  or 
(3)  changed  into  fats  and  deposited  in  body,  or  (4)  in 
case  of  extra  large  amounts  which  body  cannot  handle 
the  excess  is  excreted  in  the  urine. 

One  gram  of  carbohydrate  furnishes  about  4  Calories 
of  energy  to  the  body. 

The  average  moderate  dietary  contains  about 
500  grams  (water  free)  carbohydrate  per  day. 


CHAPTER  XXXIII. 
FATS. 

IT  will  be  remembered  that  the  organic  acids : 

OH  H    OH 

I  I       I 

formic  (H C=O),  acetic  (H C C=O), 


H 


propionic 


etc.,  were  described  as  being  the  first  three  of  a  series 
of  acids  increasing  in  complexity.  This  series  is  the 
fatty  acid  series,  so  named  because  these  acids  occur  in 
animal  and  vegetable  fats  in  combination  with  other 
substances. 

In  the  discussion  of  alcohols,  glycerine  was  men- 
tioned as  being  a  tri-atomic  alcohol  (having  three 
hydroxyl  groups): 

OH  OH  OH 

I     I 


Now  we  are  allowed  to  arrange  this  molecule  in 
space  in  any  position  we  choose  so  long  as  the  relative 


184 


FATS 


position  of  one  group  to  another  remains  the  same. 
Thus  we  may  write  glycerine  as  follows: 


H— o — c — H 


H 


Suppose  now  we  place  an  acid  with  a  carboxyl 
(COOH)  group  near  each  hydroxyl  group.  It  will 
be  remembered  that  when  two  hydroxyl  groups  ap- 
proach one  another  in  a  chemical  reaction  they  unite 
and  split  off  water,  leaving  the  groups  to  which  they 
were  attached  united  by  the  free  bonds  thus  liberated. 

*      H 


H3C— C— jOHH:— O- 

Acetic  acid. 
O 


-II 


H3C- 


-i  OH  H  i— O— C— H 


Acetic  acid. 
O 

II 

H3C— C— ;  OH  H ; 

Acetic  acid. 


II 


1  molecule  of 
glycerine. 


Here  three  molecules  of  acetic  acid  (vinegar)  com- 
bine with  one  molecule  of  glycerine.  Three  parts  H2O 
are  split  off  and  a  simple  fat  is  formed.  The  formula 
for  this  fat  is 

CH2O.OC.CH3 
CHO  .OC.CHs 
CH2O.OC.CH3. 


-  THE  BODY  FATS  185 

We  have  seen,  then,  that  a  fat  is  a  chemical  com- 
bination of  glycerine  (glycerol)  with  three  molecules 
of  some  fatty  acid.  Observing  the  formula  just  given, 
and  remembering  the  graphic  formula  of  the  paraffin 
series,  we  realize  that  the  three  CH3  groups  may  be 
supplemented  by  successive  additions  of  CH2  groups. 
In  other  words  we  can  place  as  many  CH2  groups 
between  HOOC--  and  — CH3  as  we  wish.  Accom- 
plishing this,  suppose  we  stop  at  sixteen  groups,  thus 
arriving  at  the  formula: 

CH2O.OC(CH2)16.CH3 

CHO  .OC.(CH2)i8.CH3 

CH2O.OC.(CH2)i6.CH3 

which  happens  to  be"  the  composition  of  one  of  the 
body  fats  stearin.    Stearic  acid  is  CH3  (CH2)i6.COOH. 

THE  BODY  FATS. 

The  animal  fats  consist  largely  of  mixtures  of  three 
different  fats:  stearin,  palmitin,  and  olein. 

Stearin. — Stearin  is  the  hardest  and  most  insoluble 
of  the  body  fats.  It  is  practically  insoluble  in  water 
but  goes  into  solution  in  alcohol  and  ether.  It  is  the 
fat  which  makes  tallow  solid.  Vegetable  fats '  also 
contain  it. 

Palmitin. — Palmitin  is  also  a  solid  fat  and  is  present 
in  animal  fats  in  larger  amounts  than  stearin.  There 
are  two  CH2  groups  less  in  palmitic  acid  than  in  stearic, 
that  is,  its  formula  is  CH3.(CH2)i4.COOH. 

Olein. — Olein  occurs  in  greater  quantities  in  vege- 
table fats  than  in  animal  fats,  although  it  is  present 


186  FATS 

in  all  animal  fats.  At  ordinary  temperature  it  is  a 
colorless  oil,  lighter  than  water.  It  is  not  exactly 
like  stearin  and  palmitin  in  composition,  for  some 
of  the  carbon  atoms  have  only  one  H  and  are,  hence, 
bound  to  the  next  C,  by  two  bonds,  thus 

H   H 

I     I 
— c=c— . 

We  call  oleic  acid  an  unsaturated  acid  because  it  takes 
up  chlorine,  bromine,  iodine,  and  other  elements  so 
easily. 

VEGETABLE  FATS. 

Olive  oil,  cottonseed,  peanut,  and  corn  oil,  etc.,  are 
mixtures  of  various  fats,  hence  their  relation  to  the 
animal  body  is  essentially  the  same  as  that  of  animal 
fats. 

SOAPS. 

If  fats  are  boiled  with  lye  there  is  evidently  a  chemical 
change,  for  the  two  substances  lose  their  identity  and 
two  new  substances  appear,  namely,  soap  and  glycerine. 
On  analysis  we  find  that  the  soap  is  a  combination 
of  the  alkali  (sodium)  with  the  fatty  acid  forming  a 
salt.  For  example,  the  stearin  would  form  sodium 
stearate  CH3(CH2)i6.COONa..  The  OH  of  the  lye 
(NaOH)  went  to  replace  that  lost  in  the  glycerine 
when  it  was  joined  to  the  fatty  acid  to  make  the  fat. 
Any  of  the  metals  capable  of  combining  to  form  salts 
can  be  combined  with  a  fatty  acid  to  form  a  soap. 
Most  of  the  soaps,  except  sodium  and  potassium,  are 
insoluble  in  water  and,  hence,  useless  for  cleansing, 


FOOD  VALVE  OF  FATS  187 

although  they  may  be  used  medicinally  as  ointments. 
The  process  of  breaking  up  a  fat  to  form  a  soap,  setting 
free  glycerine  is  known  as  saponification  (saponis, 
Latin  =  soap;  facio  =  to  make). 

Soaps  clean  greasy  substances  by  emulsifying  the 
fats  so  that  water  will  remove  them. 

THE  DIGESTION  OF  FATS. 

The  digestion  of  fats  does  not  begin  until  the  food 
has  passed  from  the  stomach  into  the  intestine. 
Here  fat  digestion  proceeds  in  two  different  steps: 

(1)  the  pancreatic  juice  and  the  bile  emulsify  the  fats; 

(2)  an  enzyme  (lipase)  of  the  pancreatic  juice  hydro- 
lyzes  the  fats  into  glycerine  and  fatty  acids. 

These  are  absorbed  by  certain  cells  in  the  mucous 
membrane  of  the  intestine,  and  it  is  thought  they  are 
built  up  to  form  body  fats  before  being  taken  into  the 
blood  stream. 

The  newly  formed  body  fats  are  stored  in  various 
parts  of  the  body  until  needed  for  energy  production. 

FOOD  VALUE  OF  FATS. 

Fats  are  burned  in  the  body,  furnishing  heat  and 
forming  C02  and  H2O.  Having  less  oxygen  in  the 
molecule  in  proportion  to  carbon  and  hydrogen  than 
is  found  in  carbohydrates,  they  require  more  oxygen 
from  the  air  for  the  same  amount  of  CO2  given  off. 
Therefore,  by  determining  the  amount  of  oxygen 
consumed,  the  amount  of  CO2  and  heat  given  off,  and 
the  loss  in  weight,  we  are  able  to  ascertain  whether 


188  FATS 

carbohydrates  or  fats  are  being  oxidized  to  furnish 
body  heat. 

Calorimetric  experiments  have  shown  that  1  gram 
of  fat  yields  to  the  human  body  about  9.3  Calories. 
An  average  liberal  dietary  for  a  man  contains  about 
50  grams  of  fat  per  day. 

SUMMARY  OF  CHAPTER  XXXIII. 

Fats  are  hydrolyzed  by  superheated  steam,  forming 
glycerine  and  an  organic  acid.  One  molecule  of  gly- 
cerine (a  tri-atomic  alcohol)  is  combined  with  three 
molecules  of  some  fatty  acid  to  form  fat.  In  the 
process  three  molecules  of  water  are  lost.  In  the 
hydrolysis  these  three  molecules  of  water  must  be 
supplied. 

The  character  of  the  fat,  olein,  palmitin,  stearin, 
etc.,  depends  upon  the  fatty  acid  constituent.  The 
glycerine  is  the  same  in  all  fats. 

The  essential  part  of  vinegar,  acetic  acid,  is  the  lowest 
of  the  series  of  fatty  acids.  It  has  the  composition 
CH3COOH.  Other  members  of  the  series  are  obtained 
by  adding  CH2  or  multiples  of  this  methylene  group,  e.  g., 
CH3CH2COOH,  CH3(CH2)2COOH,  etc.  Stearic  acid 
contains  sixteen  of  these  groups:  CH3.(CH2)i6.COOH. 

The  body  fats  are  mixtures  of  stearin,  palmitin  and 
olein.  Stearin  is  the  hardest  and  most  insoluble  of  the 
body  fats.  It  has  the  highest  melting-point. 

Palmitin  is  also  a  solid  fat.  Most  of  the  body 
fat  consists  of  palmitin. 

Olein  is  fluid  at  ordinary  temperatures.     It  occurs 


SUMMARY  OF  CHAPTER  XXXIII  189 

in  larger  quantities  in  vegetable  fats  than  in  animal 
fats.  Oleic  acid  differs  from  stearic  and  oleic  acid 
in  its  inner  structure.  There  are  not  so  many  H 
atoms  in  proportion  to  the  number  of  C  atoms,  for 
some  of  the  carbon  atoms  have  only  one  H  attached 
and  consequently  they  are  attached  to  one  another  by 
a  double  bond  thus: 

H    H 

I     I 
— c=c— . 

This  kind  of  an  acid  is  said  to  be  unsatumted  because 
it  easily  absorbs  iodine,  bromine,  chlorine,  hydrogen, 
etc. 

Vegetable  fats  are  essentially  the  same  as  animal 
fats.  They  contain  greater  proportions  of  olein  and 
are  therefore  more  fluid.  It  is  apparent  that  any 
desired  consistency  of  fats  may  be  attained  by  varying 
the  proportions  of  stearin  (hard  fat)  and  olein  (fluid 
fat). 

If  fats  are  boiled  with  any  alkali,  hydrolysis  takes 
place:  glycerine  is  set  free  and  the  fatty  acid  combines 
with  the  alkali  metal  to  form  soap.  For  example, 
stearin  boiled  with  lye  forms  glycerine  plus  sodium 
stearate  (soap). 

A  soap  is  the  fatty  acid  salt  of  an  alkali.  Sodium 
and  potassium  soaps  are  soluble.  Magnesium  and 
calcium  soaps  are  insoluble.  It  is  now  plain  that 
hard  water  is  uneconomical  for  cleansing  purposes. 
Soaps  emulsify  fats  and  allow  them  to  be  removed  in 
suspension. 

Fats  are  digested  in  the  small  intestine.     The  bile 


190  FATS 

and  pancreatic  juice  emulsify  them  and  Kpase,  the 
fat  splitting  enzyme,  hydrolyzes  them  into  glycerine 
and  fatty  acid.  These  two  substances  pass  through 
the  wall  of  the  intestine  and  are  reformed  into  fats. 
Fats  are  either  burned  to  furnish  energy  or  stored 
until  needed.  Blood  serum  taken  soon  after  meals  is 
often  turbid  on  account  of  the  fat  suspended  in  it. 

Each  gram  of  fat  furnishes  about  9.3  Calories  to  the 
body  on  oxidation. 


CHAPTER  XXXIV. 
BENZENE  SERIES. 

COAL  TAR. 

WHEN  coal  is  heated  to  a  high  temperature  in  a 
vessel  from  which  all  the  air  is  excluded,  three  classes 
of  substances  are  formed:  (1)  substances  which  are 
gaseous  at  ordinary  temperature  called  illuminating 
gas;  (2)  substances  gaseous  at  high  temperatures,  but 
liquid  at  ordinary  temperatures  called  coal  tar;  and 
(3)  is  the  solid  residue  coke. 

It  is  the  second  class,  coal  tar,  which  merits  our 
interest.  From  it  are  obtained  the  raw  materials  for 
many  well-known  substances.  Many  drugs  like  acet- 
anilid,  phenacetin,  etc.,  aniline  dyes  and  perfumes 
and  other  complex  derivatives  are  obtained  from  this 
black,  tarry,  viscous,  repelling  liquid. 

If  coal  tar  is  distilled  and  the  condensed  products 
collected  in  water  a  separation  can  be  made  into  two 
classes  of  substances:  those  lighter  than  water  and 
those  heavier  than  water.  Of  course  the  lighter  oils 
rise  to  the  surface  of  the  water  where  they  may  be 
collected.  One  notices  the  odor  of  carbolic  acid  and 
finds  that  on  washing  with  lye  that  this  odor  is  removed 
and  that  the  liquid  is  clearer  and  has  a  more  pungent 
odor.  Bv  distilling  this  carefully  and  collecting  the 


192  BENZENE  SERIES 

portions  which  come  over  at  certain  temperatures, 
the  liquid  may  be  divided  into  several  fractions  which 
possess  different  boiling-points  and  specific  gravities, 
as  well  as  differ  in  their  chemical  constitution. 


BENZENE. 

The  lowest  member  of  the  series  is  commonly  known 
as  benzene  (not  the  benzine  which  is  obtained  from 
petroleum).  It  is  a  colorless  liquid,  having  a  character- 
istic odor,  boils  at  80°,  and  burns  with  a  luminous 
flame. 

Chemical  Properties. — By  analysis  it  is  found  that 
carbon  and  hydrogen  are  present  in  the  ratio  of  1  to  1, 
that  is,  one  atom  of  carbon  to  one  atom  of  hydrogen. 
The  formula  then  may  be  CH  or  any  multiple  of  this. 
The  molecular  weight  determination  tells  us  that  the 
molecule  weighs  about  103  times  as  much  as  hydrogen, 
therefore  the  formula  must  contain  six  CH  groups. 
(C  =  12,  H  =  1.08,  CH  =  13.08.  103  -h  13.08  =  about 
6.)  Then  the  formula  must  be  (CH)6  or  C6H6.  Accord- 
ing to  our  conception  of  the  combinations  of  carbon  and 
hydrogen  in  chain  formation,  there  ought  to  be  more 
hydrogens  present  to  satisfy  the  C  atoms.  A  C6 
chain  would  contain  14  H's.  Therefore,  some  of  the 
carbon  atoms  are  not  satisfied  by  H  atoms,  and  since 
all  the  carbon  atoms  seem  to  be  satisfied  (benzene 
is  not  very  active  chemically),  they  must  be  joined 
to  one  another  in  certain  places.  The  valence  of  carbon 
is  four.  Taking  all  these  facts  into  consideration 


BENZENE  193 

with  many  others,  a  different  arrangement  of  the  C 
and  H  atoms  have  been  arrived  at,  namely,  a  ring 
formula : 


H— C  C— H 

I  II 

H— C  C— H 

\    / 
C 

I 
H. 


This  is  known  as  the  benzene  ring. 

It  is  without  the  sphere  of  present  considerations 
to  discuss  the  methods  of  experimentation  and  reason- 
ing by  which  this  formula  was  deduced.  It  suffices 
to  say  that  it  offers  the  best  explanation  for  the  phenom- 
ena observed  in  work  with  this  very  interesting  com- 
pound. It  may  be  worth  while  to  mention  the  effect 
of  the  halogens  on  benzene.  In  the  sunlight  a  mixture 
of  benzene  and  bromine  unite  to  form  a  series  of 
brom-benzenes,  mono-,  di-,  tri,  etc.,  up  to  six.  They 
have  the  formulas  C6H5Br,  C6H4Br2,  CeHsBrs,  etc., 
from  which  it  will  be  seen  that  in  each  instance 
the  bromine  replaces  the  H  atoms.  The  same  thing 
is  true  when  the  various  nitrates  of  benzene  are 
prepared. 

Does  it  matter  which  H  is  replaced?  Any  number 
of  monobrom-  or  mono-nitro-benzenes  have  been 
prepared  and  in  all  instances  they  were  identical, 
showing  that  all  the  H  atoms  have  the  same  relation 
to  the  ring.  If  now  we  form  di-brom-  or  di-nitro-ben- 
13 


194  BENZENE  SERIES 

zenes  we  begin  to  observe  differences  in  them.     For 
example  : 


N02 

C 

/  \ 

H—  C  C—  NO2 

I  II 

H—  C  C—  H 

\    / 
C 

I 
H 


has  different  physical  properties  from 


NO2 

I 
C 

/   \ 
H—  C  C—  H 

I  II 

H—  C  C—  NO2 

\    / 
C 

H 


and  still  another  di-nitro-benzene  has  different  proper- 
ties from  either: 

NO2 

C 

/-   \ 
H—  C  C—  H 

I  II 

H—  C  C—  H 

\    / 

C 

I 

N02 

thus  showing  that  the  relative  positions  of  the  groups 
to  one  another  make  differences  in  the  chemical  com- 


BENZENE  195 

pounds.  These  positions  have  names:  numbering  the 
top  C  as  1  and  proceeding  clockwise,  we  observe  that 
in  the  first  compound,  the  hydrogen  attached  to  1 
and  2  were  replaced  (this  is  called  or^o-di-nitro-ben- 
zene,  or  the  two  nitro  groups  are  said  to  be  ortho  to 
one  another).  In  the  second  example  1  and  3  were 
replaced,  thus  producing  a  meta  compound,  and  in  the 
third  example  1  and  4  were  replaced,  making  para- 
di-nitro-benzene. 

Benzene  is  one  of  the  most  important  compounds 
because  it  is  the  foundation  of  a  large  series  of  highly 
interesting  and  important  substances  found  in  medicine 
and  physiology. 

Substitution  Products  of  Benzene. — Phenol. — It  was 
stated  that  the  lighter  oils  from  which  benzene  was 
prepared  had  the  odor  of  carbolic  acid.  It  has  been 
found  that  carbolic  acid  does  occur  in  both  the  first 
and  the  second  separations  and  can  be  recovered  in  a 
pure  crystalline  state.  Enquiring  into  the  chemical 
constitution  of  carbolic  acid  it  has  been  found  that 
it  is  a  benzene  in  which  one  of  the  H  atoms  has  been 
replaced  by  a  hydroxyl  group,  having  the  formula 
C6H5— OH  or 

OH 

I 
C 

/   \ 
H— C  C— H 

I  II 

H— C  C— H 

\    / 
C 

H. 


196  BENZENE  SERIES 

From  our  knowledge  of  the  methane  series  it  would 
appear  that  carbolic  acid  could  be  made  from  benzene. 
We  can  prepare  mono-brom-benzene  in  the  method 
already  given.  Boil  this  with  silver  oxide  and  carbolic 
acid  is  formed  (compare  preparation  of  methyl  alcohol 
from  methane,  page  144).  From  the  resulting  mixture 
carbolic  acid  can  be  crystallized. 

Thus  carbolic  acid  is  not  an  acid  at  all.  Instead  of 
an  organic  acid  group  (COOH)  it  contains  a  hydroxyl 
group  (OH)  making  it  an  alcohol.  It  should  not  be 
called  carbolic  acid:  phenol  is  the  proper  name  and 
suitable  because  it  signifies  that  a  phenyl  group  (Cells) 
is  joined  to  an  alcohol  group  (ol  signifies  an  alcohol). 

Properties — Phenol  crystallizes  in  beautiful,  clear, 
colorless  needles,  which  develop  a  brownish-red  color 
on  exposure  to  light  over  a  long  period.  It  is  soluble 
in  alcohol  and  ether.  Saturation  in  water  yields  a  5 
per  cent,  solution. 

Phenol  is  a  protoplasmic  poison  and  for  that  reason 
is  used  as  an  antiseptic  and  germicide.  It  is  interesting 
to  note  that  phenol  was  the  first  antiseptic  used  in 
surgery.  Lister,  the  founder  of  antiseptic  surgery,  used 
it  in  such  great  quantities  that  he  himself  and  his 
assistants  developed  phenol  poisoning. 

Caustic  soda  unites  with  phenol  to  form  sodium 
phenolate,  CeHsO.Na.1  Similar  compounds  are  formed 
by  potassium,  barium,  etc.  Sulphates  form  a  loose 
compound  with  phenol,  and  ethyl  alcohol  neutralizes 

1  Sodium  phenolate  is  not  hydrolyzed  by  water  into  NaOH  and 
phenol,  as  we  would  expect  if  phenol  corresponded  exactly  to  an  ordi- 
nary alcohol  ate.  The  presence  of  the  phenyl  group  then  confers  some 
sort  of  acidic  properties  to  the  alcohol  group. 


BENZENE  197 

its  poisonous  effects.  Therefore,  alcohol  or  any  soluble, 
non-poisonous  sulphate  forms  the  logical  antidote  in 
cases  of  poisoning  by  phenol. 

Toluene. — It  ought  to  be  possible  to  substitute  a 
methyl  group  for  any  of  the  H  atoms  of  benzene. 
This  has  been  done,  and  the  natural  product  having 
identical  composition  is  also  found  in  the  light  oil 
obtained  from  the  coal  tar.  This  is  toluene  and  has 

the  formula : 

CH3 

c 

/  \ 

H— C  C— H 

I  II 

H— C  C— H 

\   / 
C 

H. 

It  is  slightly  heavier  than  benzene  and  not  so  volatile. 
It  is  added  in  experiments  in  physiological  chemistry 
to  prevent  bacterial  growth.  It  inhibits  ferment 
action  to  a  slight  extent. 

Xylene. — The  next  product  in  the  benzene  series  is 
xylene,  which  is  di-methyl  benzene;  that  is,  two  of  the 
hydrogen  atoms  are  replaced  bv  methyl  groups.  One 
formula  is 

CH3 

I 
c 

/  \ 

H— C  C— CH3 

I  II 

H— C  C— H 

\   / 
C 

H. 


198  BENZENE  SERIES 

Of  course  there  are  two  other  possibilities  as  in  the  case 
of  the  nitro-benzenes.  Xylene  is  heavier  than  toluene 
and  boils  at  a  higher  temperature.  It  is  used  as  a 
dehydrating  agent  in  treating  pathological  sections 
and  also  to  clean  cedar  oil  from  lenses.  Xylene  dis- 
solves paraffin  very  easily. 

Other  Members  of  the  Benzene  Series  differ  in 
the  number  of  hydrogen  atoms  replaced  by  methyl 
groups.  They  are  of  interest  to  the  organic  chemist. 

Cresols.  —  The  alcohol  of  toluene  corresponding  to 
phenol  (the  alcohol  of  benzene)  is  known  as  cresol. 
Several  of  these  alcohols  are  possible  according  to  the 
position  of  the  alcohol  group.  The  cresols  are  antiseptic 
and  find  use  in  practical  disinfection. 

ALDEHYDES   OF   THE   BENZENE   SERIES. 

Benzaldehyde.  —  Just  as  we  have  aldehydes  of  the 
methane  series,  so  there  are  aldehydes  of  the  benzene 
series.  Remembering  that  the  group  —  CHO  is  charac- 
teristic of  the  aldehydes,  benzaldehyde  would  be 


CHO 

1 

C 

/p      \ 

H—  C 

XC—  H 

I 

II 

H—  C 

C—  H 

\    / 

/ 

C 

1 

H. 

The  relation  to  benzene  is  apparent.     Of  course  the 
aldehyde  can  not  be  formed  directly  from  the  benzene 


SUMMARY  OF  CHAPTER  XXXIV  199 

by  oxidation  because  another  C  atom  is  necessary.  It 
is  therefore  necessary  to  use  the  methyl  substitution 
product  (toluene)  for  oxidizing,  to  obtain  benzaldehyde. 
This  is  the  substance  lending  the  peculiar,  pungent 
odor  to  bitter  almonds.  Benzaldehyde  is,  therefore, 
called  "oil  of  bitter  almonds." 

Benzole  Acid. — Much  interest  has  been  attached 
in  late  years  to  benzoic  acid  on  account  of  its  use 
as  a  preservative  in  certain  foodstuffs.  It  may  well 
be  called  a  coal-tar  derivative,  because  it  can  be 
obtained  by  oxidizing  toluene.  It  is  found  in  gum 
benzoin,  and  certain  balsams.  It  crystallizes  in  white 
needles  or  plates. 

The  constitution  of  benzoic  acid  is: 

COOH 

c 

/  \ 

H— C  C— H 

I         I! 

H— C  C— H 

\    / 
C 

H. 

Taken  into  the  body  it  is  excreted  in  the  urine  in 
combination  with  amino-acetic  acid,  forming  hippuric 
acid.  The  latter  occurs  normally  in  the  urine  of  horses 
and  cows. 

SUMMARY  OF  CHAPTER  XXXIV. 

Coal  tar  results  from  the  air-free  distillation  of  coal. 
Coal  tar  contains  a  large  number  of  substances  which 


200  BENZENE  SERIES 

form  the  basis  of  the  manufacture  of  drugs,  dyes,  per- 
fumes, and  other  chemicals. 

Coal  tar  may  be  redistilled  and  by  condensing  it 
into  water  two  portions  are  collected:  one  lighter  than 
water,  the  other  heavier.  Both  of  these  portions 
may  be  fractionally  distilled  and  various  compounds 
separated. 

Benzene  is  a  light,  colorless  liquid  found  in  the 
lighter  portion.  By  analysis  benzene  has  been  found 
to  be  composed  of  (CiHi).  Molecular  weight  deter- 
minations show  the  relative  weight  of  the  molecule 
is  103.  Then  mol.  wt.  of  CH  (13.08)  divided  into  103 
gives  about  6.  Therefore,  the  formula  of  benzene  = 
(CH)6  or  C6H6.  The  generallv  accepted  structural 
formula  is  the  ring  of  Kekule.  In  the  ring  formula 
each  H  atom  bears  the  same  relation  to  the  molecule. 
The  H  atoms  may  be  replaced  by  halogens  forming 
compounds  like  C6H5C1,  C6H4C12,  etc.,  up  to  CC16. 

The  H  atoms  may  be  replaced  by  NO2  groups  to 
the  same  extent.  All  mono-nitro  benzenes  possess  the 
same  characteristics,  but  there  are  three  different 
di-nitro-benzenes.  Nitro  groups  replacing  H  atoms 
next  to  one  another  form  ortfAo-nitro-benzene;  if  one 
Holies  between  them  a  meta  compound  results,  and 
if  two  H  atoms  lie  between  them  a  para  compound 
results.  Ortho,  meta,  and  para  refer  to  position.  These 
names  are  not  restricted  to  nitro  compound;  they 
apply  to  other  substitution  products  as  well. 

Phenol  is  hydroxy  benzene  C6H5OH.  It  is  really  an 
alcohol  and  not  an  acid,  though  phenol  seems  to  possess 
more  affinity  for  bases  than  ordinary  alcohols  (see  note 


SUMMARY  OF  CHAPTER  XXXIV  201 

page  196).  Carbolic  acid  is  an  erroneous  name  for 
phenol.  Phenol  can  be  prepared  from  benzene  by  the 
same  process  in  which  methyl  alcohol  is  produced  from 
methane. 

Toluene  is  methyl  benzene,  i.  e.,  one  of  the  H  atoms 
is  replaced  by  a  methyl  group  (CH3). 

Xylene  is  di-methyl-benzene.  Two  H  atoms  are 
replaced  by  methyl  groups.  Here  again  three  xylenes 
are  possible — ortho,  meta,  and  para. 

Benzaldehyde  is  commonly  known  as  oil  of  bitter 
almonds.  It  is  benzene  in  which  an  H  atom  has  been 
replaced  by  an  aldehyde  group,  —  CHO. 

Benzoic  acid  occurs  in  gum  benzoin  and  balsams. 
It  can  be  made  by  oxidizing  toluene  or  benzaldehyde. 
Instead  of  an  aldehyde  group  as  in  benzaldehyde  there 
is  an  acid  group  (carboxyl,  COOH)  replacing  an  H 
atom. 


CHAPTER  XXXV. 

NITROGEN,  N. 
(At.  wt.  =  14.) 

NITROGEN  is  an  element  of  great  importance.  It  is 
involved  in  all  branches  of  chemistry. 

Occurrence. — Nitrogen  is  present  to  some  extent 
in  all  living  matter:  it  is  one  of  the  principal  elements 
in  the  living  cell.  Approximately  four-fifths  of  the 
air  is  free,  inert  nitrogen. 

Properties. — Nitrogen  belongs  in  the  same  group 
with  arsenic,  antimony,  phosphorus,  and  bismuth.  It 
is  a  tasteless,  colorless,  odorless  gas  characterized  by 
its  extreme  inertness,  even  at  high  temperatures.  The 
nitrogen  of  the  air  is  so  inactive  chemically  that  it  is 
only  with  great  difficulty  that  it  can  be  made  to  com- 
bine with  other  elements.  This  has  been  accomplished, 
however,  by  means  of  electric  sparks.  Certain  bacteria 
which  grow  on  the  roots  of  clover,  peas,  etc.,  seem  to 
fix  atmospheric  nitrogen  with  such  ease  that  they  serve 
to  fertilize  the  soil.  Such  crops  are  often  planted  in 
rotation  and  cultures  of  nitrogen-fixing  organisms 
sown  on  the  soil. 

Compounds  of  Nitrogen. — Nitrogen  occurs  in  the  air 
as  N2.  On  passing  an  electric  spark  through  a  mixture 
of  nitrogen  and  hydrogen,  ammonia  is  formed.  This 
has  the  composition  NH3,  showing  us  that  nitrogen  is 
trivalent,  although  at  times  it  is  pentavalent. 


SALTS  OF  AMMONIA  203 

Properties  of  Ammonia. — Ammonia  dissolves  in  water, 
forming  ammonia  water  (NH4OH)  or  ammonium  hydrox- 
ide. In  this  state  it  is  active  chemically  like  an 
alkali,  the  group  NH4  corresponding  to  a  metal  united 
with  a  hydroxyl  group.  Ammonia  is  an  irritating, 
penetrating  gas,  readily  detected  even  in  small  quanti- 
ties in  the  air.  The  effect  on  the  skin  and  eyes  is  such 
that  strong  solutions  should  be  handled  with  care. 

Ammonia  can  be  liquefied  by  pressure.  In  returning 
to  the  gaseous  state  it  absorbs  large  amounts  of  heat. 
This  fact  is  utilized  in  modern  ice-making  and  refrigerat- 
ing machines.  The  ammonia  is  liquefied  by  compres- 
sion and  cooled  by  tap  water.  It  is  then  allowed  to 
expand  into  large  pipes  coiled  in  brine.  The  brine  is 
thus  cooled  and  circulated  by  pumps. 

Salts  of  Ammonia. — Ammonium  hydroxide  neutralizes 
acids  with  the  production  of  salts,  as  for  example, 
ammonium  chloride,  ammonium  sulphate,  ammonium 
acetate,  etc.  These  salts  are,  as  a  rule,  very  soluble 
in  water,  are  white  crystalloids  and  are  volatile.  In 
medicine  they  are  administered  as  heart  stimulants 
and  expectorants.  There  are  certain  double  salts  of 
interest  to  the  analytical  and  research  chemist. 

The  reaction  between  acetic  acid  and  ammonia  will 
interest  us  on  account  of  its  bearing  on  the  chapter  to 

follow. 

H  H 

I  I 

NH4OH  +  H— C.COOH  =  H— C.COO.NH4  +  H2O. 

I  I 

H  H 

Ammonium 
acetate. 

Notice  the  position  of  the  ammonium  group. 


204  NITROGEN 

Amino-acids. — By  treating  acetic  acid  with  bromine 
the  hydrogens  of  the  methyl  group  (CH3)  are  succes- 
sively replaced  by  bromine.  The  first  reaction  is  as 
follows: 

Br 

I 

CH.sCOOH  +  Br2  =  H— C.COOH  +  HBr. 

H 

Mono-brom-acetic  acid. 

If,  now,  we  treat  one  molecule  of  this  substance  with 
two  molecules  of  ammonia  we  find  that  the  ammonia 
will  combine  with  the  bromine  to  form  ammonium 
bromide,  leaving  an  unsaturated  bond  which  will  take 
up  the  other  molecule  of  ammonia. 

Br  NH2 

H— C.COOH  +  2NH4OH  =  H— C.COOH  +  2H2O  +  NH4Br. 

I  '    I 

H  H 

Amino-acetic  acid. 

This  substitution  product  in  a  fatty  acid  is  of  very 
great  importance  in  physiological  chemistry  because  of 
the  relation  of  these  acids  to  proteins  .(the  chief  con- 
stituents of  living  cells). 

Amino-acetic  acid  is  the  representative  of  a  class. 
Going  back  to  the  study  of  fatty  acids  it  will  readily 
occur  to  one  that  there  are  many  such  compounds 
possible.  For  instance,  the  fatty  acids  higher  in  the 
scale  of  complexity  (containing  more  methyl  groups), 
as  propionic,  butyric,  etc.,  acids  may  contain  amino 
groups  in  the  place  of  hydrogens  of  the  methyl  groups. 
There  are  other  possibilities:  we  have  learned  that 


OCCURRENCE  205 

the  relative  positions  of  groups  make  considerable 
differences  in  the  chemical  as  well  as  physical  proper- 
ties of  substances.  Then  the  amino  group  (NH2) 
may  replace  different  hydrogen  atoms.  Also,  the 
occurrence  of  two  or  three  or  four  amino  groups  in 
higher  fatty  acids  gives  us  the  corresponding  di,  tri, 
etc.,  amino-acids. 

Properties. — Amino-acids  are  crystallizable,  bodies 
possessing  various  degrees  of  solubility.  They  may 
be  decomposed  by  nitrous  acid  giving  off  nitrogen 
and  forming  the  corresponding  hydroxy  acid — e.  g., 
CH2OH.COOH. 

Amino-acids  act  both  as  bases  and  acids.  The 
hydroxyl  group  in  the  carboxyl  (COOH)  group  makes 
it  acid  in  reaction  and  it  therefore  reacts  with  metals 
to  form  amino  salts  of  that  metal;  for  example,  zinc 
aminoa-cetate  is 

X)OC.CH2.NH2 
Zn< 

XOOC.CH2.NH2. 

These  salts  also  unite  with  other  salts  to  form  double 
salts.  The  basic  properties  are  shown  by  the  fact 
that  amino-acids  combine  with  acids  to  form  double 
compounds  like  the  following: 

NH2.HC1 

I 

CH2.NH2.COOH  +  HC1  =  H— C.COOH. 

H 

Occurrence. — Amino-acids  occur  normally  in  the 
urine.  Any  decomposition  of  meat  by  digestive 
ferments  or  bacterial  action  sets  free  amino-acids, 


206  NITROGEN 

consequently  they  are  found  in  the  intestine  and  in 
the  blood  stream  of  the  portal  circulation.  It  will 
appear  later  that  the  extent  of  digestion  and  the 
place  where  it  occurs  can  be  studied  by  determining 
among  other  things  the  amino-acids. 

SUMMARY  OF  CHAPTER  XXXV. 

The  element  nitrogen  belongs  in  the  same  chemical 
group  as  arsenic,  antimony,  phosphorus,  and  bismuth. 
However,  it  has  no  physical  properties  in  common  with 
these  elements. 

Nitrogen  is  an  odorless,  colorless,  inert  gas.  Four- 
fifths  of  the  air  consists  of  this  inert  element  which 
serves  to  dilute  the  oxygen. 

It  is  with  considerable  difficulty  that  nitrogen  is 
made  to  combine  with  other  elements.  Even  at  high 
temperatures  it  resists  union,  though  there  are  certain 
bacteria  which  grow  on  the  roots  of  clover,  beans  and 
peas,  capable  of  fixing  atmospheric  nitrogen.  Electric 
sparks  also  are  able  to  fix  it.  Under  pressure  at  high 
temperatures  in  the  presence  of  the  proper  activat- 
ing agent,  nitrogen  combines  with  hydrogen  to  form 
ammonia,  NH3. 

Ammonia  gas  dissolves  in  water  to  form  ammonium 
hydroxide.  This  compound  acts  chemically  like  an 
alkali,  forming  salts  with  acids.  Ammonia  and  ammo- 
nium hydroxide  are  caustic  to  the  skin  and  mucous 
membranes. 

Compressed  ammonia,  allowed  to  expand  into  large 
pipes,  absorbs  large  amounts  of  heat.  Advantage  is 
taken  of  this  property  in  refrigerating  processes. 


SUMMARY  OF  CHAPTER  XXXV  207 

Ammonium  salts  appear  as  other  crystalloids.  They 
are  very  easily  soluble  in  water  and  are  volatile. 

NH2  is  called  the  amino  group.  Nitrogen  has  a 
valence  of  three  or  five.  The  amino  group  has  a  valence 
of  one,  since  two  of  the  three  bonds  of  the  nitrogen 
are  satisfied  by  hydrogen  atoms. 

An  amino  group  may  be  substituted  for  one  of  the 
H  atoms  in  the  methyl  groups  of  fatty  acid.  Such  a 
substitution  product  is  called  an  amino-acid.  Amino- 
acetic  acid  has  the  formula  CH2.NH2.COOH. 

Amino-acids  are  crystalloids.  They  are  decom- 
posed by  nitrous  acid,  setting  free  nitrogen,  leaving 
the  corresponding  hydroxy  acid  as  CH2OH.COOH. 
(hydroxy  acetic  acid  or  gly colic  acid).  Amino-acids 
act  both  as  acids  or  bases,  i.  e.,  they  form  salts 
and  double  salts  with  metals.  They  also  combine 
directly  with  acids,  e.  g.,  amino-acetic  hydrochloride, 
CH2.NH2.HC1.COOH. 

Amino-acids  occur  in  the  products  of  digestion,  in 
the  blood  and  various  tissues  of  the  body,  and  in  the 
urine. 

Digestive  processes  of  proteins  may  be  followed 
to  some  extent  by  studying  the  liberation  of  amino- 
acids.  Amino-acids  are  the  chief  constituents  of  pro- 
teins (egg  white,  casein  of  milk,  gluten  of  wheat,  etc.). 


CHAPTER  XXXVI. 
OTHER  NITROGEN  COMPOUNDS. 

Cyanogen. — If  potassium  carbonate  and  charcoal 
are  heated  together  in  a  closed  vessel  in  the  presence 
of  ammonia  gas  the  following  reaction  takes  place: 

K2CO3  +  C  +  2NH3  =  2KCN  +  3H2O. 

KCN  is  potassium  cyanide,  one  of  the  most  potent 
poisons.  It  is  a  white,  crystalline  solid,  easily  soluble 
in  water.  In  water  solutions  it  dissociates  and  the 
basic  properties  of  the  potassium  are  so  much  more 
prominent  than  the  weakly  acid  reaction  of  the  CN 
group  that  the  solutions  are  alkaline  in  reaction. 

In  the  presence  of  any  mineral  acid,  like  HC1,  KCN 
is  decomposed  with  the  formation  of  hydrocyanic  gas, 
HCN.  This  is  a  poisonous  gas  with  a  character- 
istic odor.  Inhalation  of  the  gas  produces  a  choking 
sensation  and  dizziness — even  small  amounts  may 

kill. 

The  group  CN  is  called  cyanogen.  It  is  strangely 
like  chlorine,  bromine,  iodine,  and  fluorine  in  its 
chemical  behavior.  The  group  combines  with  hydro- 
gen as  we  have  seen  to  form  an  acid;  it  also  forms 
salts  with  metals  and  alcohol.  It  is  monovalent.  The 


ANILIN  209 

group  does  not  exist  alone — it  does,  however,  exist 
as  di-cyan  (CN)2. 

The  cyanogen  group  offers  a  means  for  adding  a 
carbon  group  to  a  radical.     That  is,  by  means  of  the 
CN  group  methane  may  be  converted  into  an  acid 
containing  one  C  atom  more  than  the  alcohol. 
CH4  +  12  =  CH3i  +  HI. 

CH3I  +  KCN  =  CHsCN  +  KI. 
CHaCN  +  KOH  +  H2O  =  CH3COOK  +  NH3. 
CHaCOOK  +  HC1  =  CHsCOOH  +  KC1. 
Acetic  acid. 

Sulphocyanates. — If  KCN  is  boiled  with  sulphur, 
potassium  sulphocyanate,  KCNS,  is  formed.  This 
compound  is  of  interest  because  it  occurs  in  small 
amounts  in  the  human  saliva. 

There  are  a  great  many  other  compounds  of  nitrogen 
with  carbon,  hydrogen,  and  oxygen  which  can  not  be 
discussed  here. 

Anilin. — Anilin  has  become  a  familiar  word  in  recent 
years  on  account  of  the  relation  of  this  -compound  to 
dyestuffs.  This  substance  was  first  obtained  from  the 
Indigo  plant  by  distillation.  Anilin  is  also  found  among 
the  coal-tar  products  and  may  also  be  distilled  from  bones. 
The  discovery  of  the  graphic  formula  of  this  compound 
and  its  subsequent  manufacture  from  benzene  is  one 
of  the  most  brilliant  examples  of  the  use  which  chemis- 
try has  been  to  modern  life.  Its  formula  is  C6H2NH2, 
which,  on  inspection,  appears  to  be  composed  of  an 
amino  group  replacing  one  of  the  hydrogen  atoms  in 
the  benzene  molecule.  By  chemical  analysis  this 
is  found  to  be  the  case.  In  the  preparation  of  anilin 
one  cannot  simply  add  an  amino  group  to  the  benzol 
14 


210  OTHER  NITROGEN  COMPOUNDS 

nucleus  but  must  attain  this  end  by  some  other  route. 
First  the  substitution  of  the  nitro  radical  is  brought 
about  by  the  action  of  nitric  acid  of  benzene  in  the 
presence  of  sulphuric  acid.  This  we  will  remember 
forms  nitrobenzene,  C6H5NO2.  The  general  method 
for  getting  rid  of  oxygen  is  by  reduction,  therefore, 
reducing  the  nitrobenzene  by  means  of  tin  and  hydro- 
chloric acid,  hydrogen  combines  with  the  oxygen,  form- 
ing three  parts  of  water  and  two  other  hydrogen  atoms 
enter  into  the  place  vacated  by  the  oxygen.  Anilin 
is  a  colorless  liquid  which  soon  takes  on  a  reddish 
color  after  exposure  to  air.  It  is  used  as  a  mordant  in 
bacteriological  work  and  is  the  substance  from  which 
a  great  many  of  our  coal  tar  dyes  are  made.  The  syn- 
thetic production  of  these  substances  is  so  cheap  in  com- 
parison with  the  cultivation  and  preparation  of  the 
indigo1  plant  that  practically  all  of  our  dyes  are  made 
in  the  chemical  laboratory. 

Anilin  is  very  sensitive  to  the  action  of  reagents  and 
for  this  reason  offers  many  opportunities  for  the  produc- 
tion of  substitution  products.  It  will  be  readily  seen 
that  its  constitution  is  such  that  many  substitution 
products  are  possible. 

Acetanilid. — Anilin  itself  is  a  poison  but  its  effect 
on  the  animal  body  can  be  lessened  if  other  groups  are 
attached  to  it.  For  example,  if  anilin  is  heated  with 
acetic  acid  in  an  autoclave  a  crystalline  compound  is 
formed,  which  is  used  extensively  in  medicine.  This 

1  Indigo  dye  is  made  synthetically  but  not  from  anilin.  Anilin 
dyes  are  often  used  instead  oi  indigo  dyes. 


DIAZONIUM  COMPOUNDS  211 

compound  is  a  product  of  the  combination  of  anilin 
directly  with  acetic  acid  as  follows: 

C6H5NH2  +  CHsCOOH  =  CsHsNH.OOC.CHs  +  H2O. 

Administered  in  relatively  small  doses  it  is  capable 
of  reducing  the  temperature  of  patients  with  fever  and 
is  classed,  therefore,  among  the  febrifuges  under  the 
name  of  antifebrin. 

Diazonium  Compounds. — If  anilin  hydrochloride  is 
treated  with  nitrous  acid  at  low  temperatures  a  dia- 
zonium  compound  is  formed : 


C6H5.NH2.HC1  +  NNO2  =  H— C  C— N.C1  +  2H2O 

\ 


N. 


Observe  that  one  of  the  nitrogens  has  a  valence  of 
three  and  the  other  a  valence  of  five. 

If  the  diazonium  compound  be  reduced  with  tin  and 
hydrochloric  acid  phenylhydrazin  is  formed. 
1  H 


Phenylhydrazin. 

Phenylhydrazin  is  a  colorless  liquid,  with  a  high 
index  of  refraction.  It  combines  with  aldehydes  and 

1  The  benzene  nucleus  is  often  represented  by  the  hexagon.  The 
six  carbon  and  six  hydrogen  atoms  with  the  three  sets  of  double 
bonds  are  understood. 


212  OTHER  NITROGEN  COMPOUNDS 

is  therefore  used  in  the  partial  identification  of  the 
sugars  which  contain  this  group.  Sugars  combine 
with  phenylhydrazin  to  form  characteristic  needle 
crystals.  The  melting-point  varies  according  to  the 
groups  of  sugars  entering  into  the  compound.  In  prac- 
tice in  urine  analysis,  where  it  is  desired  to  identify 
the  reducing  agent,  the  osazone  is  made.  The  osazone 
is  a  combination  of  two  molecules  of  phenylhydrazin, 
with  one  molecule  of  sugar.  Phenylhydrazin  hydro- 
chloride  (colorless  crystals)  is  generally  used.  An  excess 
of  this  salt  and  sodium  acetate  are  added  to  urine  and 
boiled.  On  cooling,  long,  yellowish  needles  form  if  sugar 
is  present.  The  needles  are  filtered  off  and  their  melting- 
point  determined. 

Alkaloids. — Such  substances  as  strychnin,  morphin, 
quinin,  atropin,  cocain,  etc.,  are  crystalline  com- 
pounds which  are  obtained  from  different  plants,  and 
which  constitute  the  active  principle  of  these  plants. 
For  example,  the  physiological  action  of  nux  vomica 
is  due  in  greater  part  to  the  presence  of  strychnin. 
These  compounds  have  very  complicated  formulas. 
They  are  called  alkaloids  on  account  of  the  fact  that 
they  are  like  alkalies  (bases)  in  forming  salts  with 
acids.  The  alkaloids  themselves  are  very  slightly 
soluble  in  water,  but  soluble  in  alcohol,  while  their 
salts  are  very  slightly  soluble  in  alcohol,  but  soluble 
in  water.  For  this  reason  alkaloids  are  usually 
administered  as  salts  rather  than  as  free  substances. 

A  great  deal  of  the  work  has  been  done  in  estab- 
lishing the  graphic  formulas  of  these  substances  with 
the  result  that  we  have  definite  knowledge  of  at  least 


VITAMINES  213 

six.  These  six  alkaloids  have  been  prepared  in  the 
laboratory,  but  on  account  of  the  expense  attached  to 
this  method  of  preparation  it  has  been  found  cheaper 
to  obtain  them  from  their  natural  sources  rather  than 
to  manufacture  them.  The  characteristic  group  of 
most  alkaloids  we  may  say  is  the  pyridin  ring: 

H 

c 
/  \ 

H— C  C— H 

I  II 

H— C  C— H 

\    / 

N. 

The  pyridin  ring  may  be  considered  as  a  benzene 
ring  with  one  of  the  CH  groups  replaced  by  N.  This 
compound,  pyridin,  may  be  made  synthetically  by 
several  processes.  It  is  found  in  bone-oil. 

Vitamines. — It  has  been  found  that  certain  nervous 
degenerations  and  disturbances  may  arise  after  the 
prolonged  administration  of  certain  diets.  For  example, 
beri-beri  can  be  produced  in  birds  by  feeding  them 
polished  rice  for  a  long  period.  Administration  of 
small  amounts  of  hulls  or  unpolished  rice  is  sufficient 
to  bring  them  back  to  normal;  even  minute  amounts 
of  extracts  of  the  hulls  or  extracts  of  yeast  seem  to 
contain  some  substance  or  substances  necessary  for 
the  normal  processes  of  the  body.  These  substances 
have  not  been  obtained  in  pure  form  and  consequently 
their  chemical  constitution  is  unknown.  They  have 
been  termed,  for  want  of  a  better  name,  "vitamines." 

Experiments  are  being  carried  on  in  many  places 


214  OTHER  NITROGEN  COMPOUNDS 

in  attempts  to  determine  the  constitution  of  these 
compounds.  It  will  be  noted  that  the  first  step  in 
determining  the  constitution  of  the  body  is  to  obtain 
it  in  crystalline  form  so  that  chemical  research  is  in  the 
ultimate  a  search  for  crystals.  So  far  the  active  prin- 
ciples classed  under  the  heading  vitamines  have  never 
been  obtained  in  crystalline  form,  so  that  we  know 
nothing  of  their  constitution. 

SUMMARY  OF  CHAPTER  XXXVI. 

Cyanogen,  CN,  is  a  group  which  acts  very  similarly 
to  the  halogens.  It  combines  with  hydrogen,  with 
metals  and  alcohols.  By  means  of  it  an  organic  radical 
may  be  oxidized  into  an  organic  acid  containing  one 
more  carbon  atom.  Methane  may  be  converted  into 
acetic  acid,  CH3COOH. 

Anilin  is  amino  benzene.  It  was  first  attained  from 
the  indigo  plant  but  is  now  synthesized  more  cheaply 
than  it  can  be  extracted  from  the  plant.  From  anilin 
a  large  number  of  dyes,  drugs,  perfumes,  etc.,  are 
synthesized. 

Anilin  is  a  poison  but  when  joined  with  an  acetyl 
group  its  poisonous  effects  are  greatly  diminished. 
Thus  acetyl  anilid  or  acetanilid  is  used  as  an  anti- 
pyretic. 

A  diazonium  compound  is  formed  by  the  action  of 
nitrous  acid  on  anilin  hydrochloride.  If  this  com- 
pound is  reduced  phenylhydrazine  is  formed.  Phenyl- 
hydrazine  is  used  to  prepare  osazones  of  sugars,  whereby 
the  latter  may  be  partially  identified.  The  melting- 


SUMMARY  OF  CHAPTER  XXXVI  215 

point  of  the  osazone  gives  a  clue  to  the  nature  of  the 
sugar. 

Alkaloids  are  the  active  principles  of  plants.  Most 
of  them  are  crystalline  substances  very  slightly  soluble 
in  water,  but  soluble  in  alcohol.  They  form  salts  with 
acids  (hence  their  name  alkaloid  =  like  alkali)  which 
are  soluble  in  water  and  slightly  soluble  in  alcohol. 
Alkaloids  are  usually  administered  as  a  salt.  Six 
alkaloids  have  been  synthesized  but  synthesis  is  more 
costly  than  extraction  from  plants.  Much  is  known 
about  several  others. 

"Vitamines"  is  a  name  given  to  a  group  of  unknown 
substances  which  appear  to  be  necessary  for  normal 
processes  of  the  body.  The  feeding  of  polished  rice 
produces  a  nerve  degeneration  known  as  beri-beri. 
Smaller  amounts  of  the  extract  of  yeasts,  or  alcoholic 
extract  of  rice  hulls  bring  about  recovery.  No  active 
crystalline  compound  has  been  isolated  from  the 
extracts.  Therefore,  these  substances  are  not  definitely 
known  but  merely  suspected. 


CHAPTER  XXXV11. 
PROTEINS. 

THE  most  important  nitrogen-containing  substances 
constitute  a  large  group  of  compounds  similar  in 
chemical  structure  and  reactions,  called  proteins. 
The  white  of  egg,  casein  (clot)  of  milk,  and  gluten  of 
wheat  are  examples  of  proteins. 

General  Characteristics. — Proteins  may  apparently 
go  into  solution,  but  it  has  been  found  that  they  do 
not  pass  through  membranes  and  collodion  sacs.  They 
are  therefore  in  colloidal  solution.  Furthermore,  some 
of  them  are  completely  coagulated  by  boiling  with  acids 
in  the  presence  of  salts.  Both  of  these  properties  are 
characteristic  of  the  colloids. 

Coagulated  proteins  evidently  undergo  some  sort 
of  change  for  they  cannot  be  redissolved  into  colloidal 
solution. 

Composition. — The  proteins  are  very  complex  in 
their  structure.  They  are  composed  of  the  elements 
C,  H,  O,  and  N,  generally  sulphur  and  sometimes 
phosphorus. 

Some  proteins  contain  iron,  and  copper  has  been 
found  in  minute  amounts  in  egg  albumen.  Iodine, 
zinc,  and  manganese  have  been  said  to  be  identified 
with  the  protein  molecule. 


OCCURRENCE  217 

The  determination  of  the  five  principal  elements 
occurring  in  proteins  shows  them  to  approximate  one 
another  very  closely  in  empirical  formulas  at  least. 
The  principal  proteins  contain  these  elements  in  about 
the  following  percentages: 

C  about  52  per  cent. 
H  about  6  per  cent. 

O  about  25  per  cent. 
N  about  15  per  cent. 
S  about  1  to  2  per  cent. 

We  have  very  little  definite  knowledge  of  the  struct- 
ure of  the  protein  molecules.  They  are  generally 
conceded  to  be  composed  of  mono-amino-acids  con- 
nected together  in  an  unknown  way.  Some  of  the 
proteins  contain  aminodextrose  (glucosamine).  The 
protein  molecule  is  very  large  but  just  how  large  has 
not  been  determined.  Known  methods  for  determin- 
ing molecular  weights  are  not  applicable  to  proteins. 
Estimates  of  the  molecular  weight  of  egg  albumen  have 
been  placed  at  5000.  The  red  blood  coloring  matter 
of  the  blood,  oxyhemoglobin,  is  estimated  to  have  a 
molecular  weight  of  about  15,000.  The  simplest  for- 
mula that  can  be  calculated  from  analyses  of  oxyhemo- 
globin is  CeBsHim,  N2o7S2FeO2io. 

Occurrence. — Proteins  are  essential  to  life.  The 
protoplasm  (protein)  of  the  cell  is  necessary  for  the 
continuance  of  life  of  the  cell.  While  fats  and  carbohy- 
drates can  be  replaced  by  one  another  and  by  proteins 
in  the  animal  economy,  the  role  of  the  proteins  cannot 
be  assumed  by  any  other  class  of  compounds. 

Vegetable  proteins  are  manufactured  from  simpler 
compounds  by  the  plants,  but  the  animal  must  depend 


218  PROTEINS 

upon  the  vegetable  kingdom  for  supply.  The  animal 
organism  is  capable  of  breaking  down  vegetable  pro- 
teins or  rebuilding  them  to  suit  the  particular  want, 
though  it  cannot  build  thein  from  inorganic  compounds. 

Varieties. — On  account  of  the  lack  of  definite  knowl- 
edge concerning  the  structure  of  proteins  and  on  ac- 
count of  the  large  variety  of  them  no  classification 
free  of  exceptions  has  been  made.  Several  classifica- 
tions have  been  advocated  by  different  associations  of 
chemists  but  these  serve  only  to  confuse  the  student 
of  elementary  physiological  chemistry.  We  may  think 
of  the  proteins  as  a  class  as  being  made  up  of  (1)  natural 
or  native  proteids,  and  (2)  changed  or  derived  proteids 
(obtained  from  1). 

We  may  classify  them  also  as:  1.  Simple  proteids. 
2.  Compound  proteids.  3.  Albuminoids. 

The  Simple  Proteids. — White  of  egg,  blood  serum, 
and  meat  are  examples  of  simple  proteids.  They  are 
coagulated  by  heat  in  slightly  acid  solution  if  salts 
are  present.  They  are  precipitated  (salted  out)  by 
saturation  with  ammonium  sulphate;  they  form  insol- 
uble albuminates  with  CuSO4,  HgCl2,  AgNO3,  and 
Pb  (OOC  •  CH3)2.  They  give  characteristic  color  reactions 
with  certain  reagents  like  nitric  acid  (xanthoproteic 
reaction,  yellow)  and  alkaline  copper  sulphate  (biuret, 
purple),  etc. 

The  chief  members  of  the  simple  proteids  are  albu- 
mins and  globulins.  Both  of  these  proteids  occur  in 
blood  serum. 

Globulins. — If  blood  serum  diluted  with  water  is 
placed  in  a  collodion  sac  which  is  allowed  to  float  in 


ALBUMINS  219 

running  water,  the  salts  from  the  blood  pass  through 
the  walls  leaving  the  proteins  behind.  Within  the  sac 
a  precipitate  forms.  This  precipitate  is  globulin. 
After  filtering  this  off,  we  find  that  globulin  is  not 
soluble  in  pure  water  but  by  the  addition  of  some  NaCl 
to  the  water,  solution  is  accomplished.  It  is  learned 
that  salts  are  necessary  for  the  solution  of  globulins. 
If  NaCl  or  even  MgSO4  is  added  to  the  globulin  solu- 
tion to  the  point  of  saturation  the  globulin  is  salted 
out.  The  same  thing  may  be  accomplished  by  adding 
an  equal  volume  of  ammonium  sulphate  (this  makes, 
of  course,  only  half  saturation  of  this  salt). 

Globulin  solutions  answer  the  tests  given  above  for 
simple  proteids.  Globulins  are  of  interest  on  account 
of  the  fact  that  the  valuable  part  of  diphtheria  anti- 
serum  is  in  the  globulin  fraction.  Indeed,  it  is  in  this 
manner  that  diphtheria  antitoxin  is  concentrated  and 
much  of  the  undesirable  and  invaluable  part  of  the 
serum  separated. 

Albumins. — In  the  dialyzing  experiment  described 
under  globulins,  it  was  found  that  after  the  globulins 
had  been  separated  there  still  remained  in  the  serum 
solution  a  simple  proteid. 

This  is  the  albumin  fraction,  which  is  soluble  in 
water  without  the  addition  of  any  salts.  Albumins 
are  precipitated  by  full  saturation  with  ammonium 
sulphate. 

Compound  Proteids. — Compound  proteids  are  com- 
posed of  a  simple  proteid  joined  to  some  non-pro teid 
substance.  They  are  classified  according  to  the 
character  of  the  non-proteid  components,  e.  g.,  glyco- 


220  PROTEINS 

proteids  yield  on  hydrolysis  a  simple  proteid  and  a 
substance  which  reduces  Fehling's  solution.  Mucin, 
the  chief  constituent  of  mucus  (secretion  of  mucous 
membranes),  belongs  to  the  class  of  glycoproteids. 
Hemoglobin,  the  red  coloring  matter  of  the  blood, 
yields  a  simple  proteid  plus  hematin  (an  iron  contain- 
ing pigment). 

The  nucleins  from  the  nuclei  of  cells  is  also  a  com- 
pound proteid. 

Albuminoids. — Albuminoids  are  substances  similar 
to  the  simple  proteids.  They  occur  in  the  horny  layer 
of  the  skin,  in  cartilage,  etc.  Gelatin  is  formed  by 
boiling  the  albuminoids  found  in  cartilage  (collagins) 
with  dilute  acid.  Gelatin  is  a  straw-colored  jelly,  when 
mixed  with  small  amounts  of  water.  It  is  soluble  in 
water  and  not  coagulated  by  boiling.  It  is  used  in 
making  plates  and  tubes  for  bacterial  growth. 

Derived  Proteids. — Protein  substances  form  acid  and 
alkali  albuminates  which  are  not  coagulable  by  heat. 
They  are  changed  chemically,  especially  the  alkali 
albuminates.  An  alkali  albuminate  may  be  formed 
from  an  acid  albuminate,  but  an  acid  albuminate  can 
not  be  formed  from  an  alkali  albuminate. 

The  Digestion  of  Proteins. — Protein  digestion  is 
begun  in  the  stomach.  The  contents  of  the  stomach 
are  kept  acid  by  the  secretion  of  hydrochloric  acid 
from  special  glands  in  the  stomach  wall.  The  degree 
of  acidity  which  these  glands  strive  to  maintain  under 
normal  conditions  is  equal  to  0.2  per  cent.  HC1.  The 
hydrochloric  acid  unites  with  the  proteins  to  form 
acid  albuminates,  and  the  protein  splitting  ferment, 


THE  DIGESTION  OF  PROTEINS  221 

pepsin,  now  begins  the  disorganization  of  the  protein 
molecule  by  breaking  off  amino-acids.  The  simplifi- 
cation of  the  protein  molecule  proceeds  through  the 
proteose  stage  until  the  protein  is  reduced  to  peptone 
plus  amino-acids.  Peptone  is  a  simplified  proteid 
(derived  proteid)  which  is  not  coagulated  by  heat. 
Its  molecule  is  smaller  and(  it  is  easily  soluble  in  water 
and  diffusible.  Peptone  is  precipitated  from  water 
solution  by  the  addition  of  several  volumes  of  absolute 
alcohol.  Gastric  digestion  proceeds  no  further  than 
the  peptone  stage  and  there  is  practically  no  absorption 
of  protein  digestion  products  from  the  stomach. 

Digestion  of  Protein  in  the  Intestines. — The  acidified 
gastric  contents  pass  into  the  small  intestine  and, 
meeting  the  bile  and  pancreatic  juices,  soon  become 
alkaline  in  reaction.  Alkaline  albuminates  are  formed 
and  the  proteins  are  further  simplified  by  trypsin, 
a  protein  splitting  ferment  secreted  in  the  pancreatic 
juice.  The  results  of  the  trypsin  digestion  of  proteins 
are  amino  acids  or  compounds  of  two  or  more  amino- 
acids.1  The  products  of  digestion  are  absorbed  and 
transported  to  some  unknown  place  by  the  blood  and 
lymph  to  be  rebuilded  into  proteins  necessary  for 
growth  and  repair.  Proteins  are  also  oxidized  in  the 
body,  yielding  4  Calories  per  gram.  It  is  not  economical 
to  furnish  heat  to  the  body  in  the  form  of  proteins, 


1  The  proteids  are  also  broken  up  in  the  intestine  to  some  extent 
by  bacteria  and  the  products  are  absorbed  and  detoxicated  in  the 
liver  and  excreted  in  the  urine.  Indican  is  one  of  these  products. 
The  bacterial  decomposition  of  proteins  are  called  putrefaction  in 
contrast  to  fermentation  which  is  the  decomposition  of  sugars.  So 
long  as  sugars  are  present  in  the  intestines  there  is  little  putrefaction. 


222  PROTEINS 

because  of  the  higher  cost  of  protein  food  and  because 
of  the  increased  metabolism  when  proteins  are  utilized. 

Excess  of  protein  is  not  stored  in  the  body,  but 
oxidized  and  excreted.  Proteins  are  necessary  for  life 
and  they  cannot  be  replaced  by  carbohydrates  or  fats. 

The  amount  of  protein  necessary  for  the  mainten- 
ance of  normal  nutrition  is  at  present  a  subject  of 
discussion.  There  are  those  who  believe  that  from 
45  to  50  grams  per  day  are  all  that  are  required  for 
maintaining  the  body  in  health.  However,  if  persons 
are  left  to  select  their  own  ration,  they  as  a  rule 
consume  more  than  twice  as  much  protein  when  it 
can  be  obtained.  Experiments  have  been  conducted, 
showing  that  the  low  protein  diet  is  sufficient  to 
nourish  the  normal  individual  when  accompanied  by 
sufficient  amounts  of  carbohydrates  and  fats,  but 
these  experiments  did  not  extend  over  a  very  long 
period  and  no  question  of  resistance  to  disease  was 
brought  up.  Too  much  protein  can  be  digested  and 
may  result  in  hardening  of  the  arteries,  kidney  lesions 
and  probably  functional  disturbances,  but  a  consider- 
able excess  of  protein  can  be  taken  daily  with  safety. 
The  trend  of  opinion  seems  to  be  on  the  side  of  the 
liberal  allowance  from  118  to  125  grams  per  day  for 
the  average  man.  Since  we  know  very  little  of  the 
mechanism  of  digestion  and  assimilation  of  these  com- 
pounds and  the  relation  of  body  proteins  to  those  pro- 
teins found  in  our  food,  it  is  perhaps  the  wiser  plan  to 
allow  the  liberal  amount  of  protein.  While  a  person 
may  remain  in  perfectly  good  health  on  a  low  protein 
diet,  we  are  not  sure  that  he  will  maintain  his  normal 
resistance  against  infecting  agents. 


SUMMARY  OF  CHAPTER  XXXVII  223 

SUMMARY  OF  CHAPTER  XXXVII. 

Proteins  are  complex,  nitrogen-containing  compounds 
occurring  as  protoplasm,  an  essential  part  of  the  cell. 
Proteins  found  in  plant  cells  have  been  synthesized 
from  the  elements.  Animal  proteins  are  derived  from 
vegetable  proteins  or  other  animal  proteins. 

Proteins  are  compounds  of  C,  H,  O,  N,  S,  Fe  and 
sometimes  P.  Little  is  known  of  their  structural 
formulas.  They  are  made  up  of  arrangements  of 
amino  acids.  Amino  glucose  occurs  in  the  molecule 
of  some  proteins.  Most  of  our  knowledge  relates  to 
the  chemistry  of  the  split  products  of  proteins  (amino 
acid  compounds).  Proteins  may  be  classified  accord- 
ing to  their  source:  (1)  natural  or  native  proteids, 
and  (2)  changed  or  derived  proteids  (obtained  from 
Class  1).  They  may  be  classified  also  as:  (1)  Simple 
proteids.  (2)  Compound  proteids.  (3)  Albuminoids. 
To  the  first  class  belong  white  of  egg,  blood  serum  and 
meat.  They  are  coagulated  by  heat  (if  salts  are 
present),  precipitated  by  acids,  by  saturation  with 
salts  and  by  certain  chemicals  like  AgNO3,  HgCl2, 
CuSO4,  Pb(OOC  •  CH3)2.  All  proteins  are  colloids,  that  is, 
they  do  not  pass  through  semi-permeable  membranes 
as  salts  do.  A  solution  of  proteins  in  a  collodion  sac 
placed  in  water  will  lose  salts  by  dialysis  into  the  sur- 
rounding water,  but  none  of  the  proteins  pass  out. 
Salts  are  necessary  to  hold  globulins  (simple  proteids) 
in  solution.  Globulins  are  found  in  blood  serum.  If 
diluted  blood  serum  is  dialyzed  the  globulin  is  pre- 
cipitated. Globulin  solutions  are  also  precipitated  by 


224  PROTEINS 

half  saturation  with  ammonium  sulphate.  Albumins 
(also  simple  proteids)  are  soluble  in  water  without 
salts.  Albumins  are  precipitated  by  complete  satura- 
tion with  ammonium  sulphate.  More  than  half  of  the 
proteins  of  blood  serum  consists  of  albumins. 

Compound  proteids  are  classified  according  to  the 
non-protein  components,  e.  g.,  glycoproteids  yield 
on  hydrolysis  a  simple  proteid  plus  a  sugar.  Mucin 
is  a  glycoproteid.  The  red  coloring  matter  of  the 
blood  is  a  compound  proteid,  consisting  of  a  simple 
proteid  and  hematin,  an  iron  containing  pigment. 

Albuminoids  are  substances  similar  to  simple  pro- 
teids. They  are  colloids  and  contain  nitrogen,  but 
proteins  can  not  be  formed  by  the  animal  body  from 
the  products  of  their  digestion.  Cartilage  contains 
albuminoids.  Gelatin  is  a  good  example.  Albumin- 
oids are  soluble  in  water  and  are  not  precipitated  by 
heat. 

Derived  proteins  are  obtained  from  proteins  by  the 
action  of  chemical  agents.  Acids  and  alkalies  unite 
with  proteins  to  form,  respectively,  acid  and  alkali 
albuminates  (derived  proteids).  They  are  soluble  in 
water  and  are  not  coagulated  by  heat. 

Protein  digestion  begins  in  the  stomach.  Acid 
albuminate  is  formed  and  broken  down  by  pepsin  to 
the  peptone  stage.  Intestinal  digestion  takes  place 
in  alkaline  solution.  The  alkaline  albuminates  are 
broken  down  to  amino-acids  by  the  trypsin  of  the 
pancreatic  juice.  The  amino-acids  are  absorbed  into 
the  blood  stream  and,  probably,  in  cells  of  the  body 
new  body  proteins  are  formed  from  them.  The  excess 


SUMMARY  OF  CHAPTER  XXXVII  225 

of  proteins  are  changed  into  urea  in  the  liver  and 
excreted  in  the  urine.  Proteins  are  not  stored  in  the 
body  except  in  growth  and  repair.  Proteins  furnish 
heat  (4  C.  per  gram)  on  oxidation  in  the  body,  but  it 
is  uneconomical  to  consume  them  for  their  heat-pro- 
ducing power.  About  125  grams  of  protein  per  day 
is  the  average  requirement.  Proteins  are  determined 
quantitatively  by  estimating  the  amount  of  nitrogen 
by  the  Kjeldahl  method  and  multiplying  total  N  by 
6.25. 


15 


CHAPTER  XXXV111. 
THE  BLOOD. 

THE  clot  which  forms  when  blood  is  drawn  encloses 
all  the  cellular  elements,  leaving  a  clear  straw-colored 
fluid  known  as  serum.  If  the  blood  is  drawn  into  oiled 
or  paraffined  tubes  it  will  remain  liquid  for  a  long 
time.  While  liquid,  the  red  and  white  cells  and  blood 
platelets  may  be  centrifuged  to  the  bottom,  leaving 
straw-colored  liquid,  which  appears  to  be  serum. 
This  is  plasma.  Plasma  is  serum  plus  the  clotting  sub- 
stance or  substances,  for  on  standing  or  on  coming 
into  contact  with  any  substance  it  can  ''wet"  the 
plasma  coagulates.  The  clot  consists  of  fibrin  and 
the  remaining  liquid  is  serum. 

Fibrin. — Fibrin  belongs  to  a  class  of  coagulated 
proteids.  It  is  the  product  of  ferment  action  on  fibrino- 
gen.  It  is  supposed  that  fibrinogen  exists  in  the  blood 
in  solution.  Fibrin-ferment  is  produced  by  the  com- 
bination of  calcium  and  an  unknown  body  called 
pro-thrombin.  Fibrin  ferment  +  fibrinogen  =  fibrin. 
Fibrin  forms  a  network  of  strands  and  includes  the 
cellular  elements  of  the  blood  in  its  meshes.  The 
coagulation  time  is  decreased  with  an  increase  in  tem- 
perature. Fibrin  may  be  obtained  by  whipping  freshly 
drawn  blood  with  a  bundle  of  wires:  the  fibrin  col- 
lects on  the  wires  and  leaves  the  cells  of  the  blood 
suspended  in  the  serum.  If  blood  is  drawn  into  sodium 


BLOOD  SERUM  227 

oxalate  or  magnesium  sulphate  the  calcium  is  precipi- 
tated and  the  blood  will  not  clot.  In  practice  blood  is 
usually  drawn  into  2  per  cent,  sodium  citrate  solution 
in  physiological  salt  solution.  It  does  not  clot,  and  the 
cells  may  be  centrifuged  down,  the  supernatant  liquid 
poured  off,  and  the  cells  washed  with  physiological  salt 
solution. 

Blood  Serum. — As  a  rule  blood  serum  is  a  clear,  pale 
yellow  to  amber-colored  liquid,  although  for  some  time 
after  meals  it  may  be  whitish  and  turbid  due  to  the 
fat  globules  in  it.  Serum  is  slightly  more  alkaline  thaji 
plasma  and  has  a  specific  gravity  of  about  1028  (1.028). 

About  9  per  cent,  of  serum  consists  of  inorganic 
salts,  most  of  which  is  NaCl.  Potassium,  magnesium, 
and  calcium  also  occur.  The  alkalinity  is  due  to  sodium 
and  potassium  carbonate  and  sodium  di-hydrogen- 
phosphate,  NaH^PCX.  About  three-quarters  of  1  per 
cent.  (0.75  per  cent.)  of  serum  is  proteid  matter  which 
consists  of  serum  globulin  and  serum  albumin.  There 
is,  perhaps,  a  little  more  albumin  present  than  globulin. 

The  salts  mentioned  above  are  evidently  necessary 
to  keep  the  globulin  in  colloidal  solution ;  if  blood  serum 
is  placed  in  a  collodion  sac  or  animal  bladder  and  this 
placed  in  a  jar  of  pure  water  the  crystalloids  (salts) 
will  pass  through  the  wall  of  the  sac1  while  the  colloids 
and  proteins  will  remain  in  the  sac.  But  the  globulin 
will  be  precipitated.  The  serum  albumin  remains  in 
solution  but  can  be  precipitated  by  complete  saturation 
with  ammonium  sulphate.  The  globulin  fraction  can 

1  This  process  is  known  as  dialysis  and  has  already  been  referred 
to  under  colloids. 


228  THE  BLOOD 

also  be  precipitated  by  passing  CO2  into  diluted  serum. 
This  method  is  used  in  the  purification  and  concen- 
tration of  diphtheria  antitoxin,  since  the  antibody  is 
contained  in  the  globulin  fraction. 

Blood  Cells. — The  blood  cells  are  mostly  red  blood  cor- 
puscles. For  every  600  red  cells  there  is  normally  one 
white  corpuscle  (leukocyte).  The  white  cells  are  larger 
than  the  red  cells  and  have  a  slightly  lower  specific 
gravity.  The  protoplasm  of  the  white  cells  consists 
of  conjugated  proteid  and  globulin.  Glycogen  (animal 
starch)  is  also  found  in  leukocytes.  The  white  cor- 
puscles have  nuclei,  while  the  red  cells  seem  to  be 
homogeneous  (i.  e.,  constant  composition  throughout). 

The  red  cells  are  very  complex  in  chemical  structure. 
Besides  globulin,  lecithin,  etc.,  these  cells  contain  the 
coloring  matter  of  the  blood,  hemoglobin.  Hemo- 
globin is  a  compound  proteid  containing  iron  and 
sulphur.  It  probably  does  not  exist  free  in  the  red  cell 
but  in  combination  with  other  proteins.  It  is  of  interest 
here  because  it  plays  the  chief  role  in  internal  respira- 
tion. Oxygen  forms  a  loose  combination  with  this 
proteid  called  oxyhemoglobin,  is  transported  to  distant 
parts  of  the  body,  and  given  up  where  needed.  Carbon 
monoxide,  CO,  forms  a  stable  compound  with  hemo- 
globin, which  cannot  be  broken  up  without  disinte- 
grating the  hemoglobin. 

Osmosis. — The  red  corpuscles  may  be  suspended  in 
serum  or  in  0.9  per  cent.  NaCl  solution  without  under- 
going appreciable  change.  If,  however,  water  is  added 
to  the  mixture  the  cells  may  be  seen  under  the  micro- 
scope to  swell  and  finally  burst.  The  suspension  of 


TONICITY  229 

red  cells  loses  its  turbidity,  becomes  clear  and  pink  in 
color,  due  to  the  solution  of  the  red  coloring  matter. 
The  swelling  of  the  red  cell  is  the  result  of  the  entrance 
of  water  into  it — osmosis.  The  same  phenomenon  can 
be  observed  by  placing  vegetable  cells  in  different 
concentrations  of  salt  solutions.  The  experiment  can 
be  carried  out  on  a  large  scale  by  filling  a  bladder  with 
a  solution  of  salt  and  placing  it  in  a  vessel  of  water. 
If  the  bladder  is  tightly  closed  it  will  finally  burst  on 
account  of  the  inflowing  of  water.  If  a  tube  had  been 
placed  in  the  neck  of  the  bladder  so  that  water  could 
rise  in  it,  the  pressure  of  the  incoming  water  can  be 
measured.  This  is  called  osmotic  pressure.  Osmotic 
pressure  may  reach  an  incredible  figure :  over  30  atmos- 
pheres (400  pounds  to  the  square  inch)  has  been 
observed. 

Many  phenomena  of  cell  life  are  explained  on  the 
basis  of  osmosis. 

It  is  interesting  to  note  that  molecular  weight  may 
be  determined  by  observing  the  osmotic  pressures 
under  certain  conditions. 

Tonicity. — Solutions  having  the  same  molecular  con- 
centration are  said  to  possess  the  same  tonicity  or  are 
isotonic.  Thus,  0.9  per  cent.  NaCl  is  isotonic  with  blood 
serum,  i.  e.,  blood  cells  placed  in  0.9  per  cent.  NaCl 
will  not  burst.  If  water  is  added  and  the  percentage  of 
NaCl  is  therefore  reduced  the  tonicity  is  lowered  and 
the  solution  is  said  to  be  hypotonic  (less  than  tonic). 
If  too  much  salt  is  present  the  solution  is  hypertonic 
(greater  than  tonic).  A  hypertonic  solution  causes 
the  red  cells  to  shrink  (crenation).  We  thus  see  the 


230  THE  BLOOD 

reason  for  preparing  physiological  salt  solution  exactly 
0.9  per  cent.  NaCl.  It  has  already  been  stated  that 
physiological  salt  solution  should  not  be  called  normal 
salt  solution  because  a  normal  (chemical)  NaCl  solu- 
tion is  a  4  per  cent,  solution.  Isotonic  (for  blood  cells) 
salt  solution  is  about  seventh  molecular,  M/7. 

Hemolysis. — The  dissolution  of  red  cells  by  water  is 
known  as  lysis,  hemolysis  or  laking.  There  are  specific 
poisons  (snake  venoms)  and  natural  agents  in  blood 
from  other  species  which  are  hemolytic.  Hemolysins 
(agents  causing  hemolysis)  can  be  called  forth  in  a 
serum  by  the  intravenous  injection  of  red  corpuscles 
of  other  animals.  For  example,  sheep  corpuscles 
injected  intravenously  into  rabbits  call  forth  a  hemo- 
lysin  capable  of  destroying  sheep  corpuscles.  This 
principle  is  used  in  the  Wassermann  reaction. 

Natural  hemolysins  potent  for  human  red  cells 
sometimes  occur  in  members  of  the  same  species.  It 
is  therefore  necessary  to  test  the  serum  of  the  donor 
against  the  red  cells  of  the  patient  before  transfusions. 

General  Characteristics  of  the  Blood. — The  Amount. 
— About  one-fourteenth  of  the  body  weight  of  man  is 
blood.  In  smaller  animals  the  amount  is  proportion- 
ally greater.  The  average  150  pound  man  has  about 
11  pounds  of  blood  or  about  five  quarts. 

Specific  Gravity. — The  specific  gravity  of  blood  may 
be  determined  by  placing  drops  of  it  in  a  mixture  of 
chloroform  and  benzol.  If  the  drop  rises  add  benzol, 
if  it  sinks  add  chloroform  until  it  comes  to  rest  about 
halfway.  The  specific  gravity  of  the  mixture  can  then 
be  determined  with  a  hydrometer — this  figure  would 


FUNCTIONS  OF  THE  BLOOD  231 

be  the  specific  gravity  of  the  blood.  The  average 
specific  gravity  is  1056  (1.056). 

Functions  of  the  Blood. — The  blood  is  the  great 
equalizer  of  the  body.  It  equalizes  heat  and  moisture, 
it  brings  food  and  oxygen  to  the  cells  and  takes  away 
CO2  and  refuse  material.  It  brings  the  protective 
agencies  to  a  point  of  injury  and  invasion  and  main- 
tains constant  guard  over  all  portions  of  the  body. 
Its  composition  is  subject  to  extreme  variation. 

Besides  gases,  the  blood  holds  liquids  in  solutions 
and  solids  in  solution  or  suspensions,  and  it  carries 
poisonous  products  to  the  liver  for  detoxication,  and 
then  again  transports  them  to  the  kidneys  for  elimina- 
tion. Urea,  uric  acid,  ammonia,  etc.,  found  in  the 
urine  are  brought  to  the  kidneys  by  the  blood. 

The  blood  receives  internal  secretions  from  the 
ductless  glands  like  the  adrenals,  the  pancreas,  the 
pituitary  body,  and  the  thyroid  gland. 

Dextrose  is  found  in  the  blood  under  normal  con- 
ditions in  about  one  to  one  and  a  half  parts  per  thou- 
sand. Whether  or  not  it  is  held  in  loose  combination 
with  some  substance  is  not  known;  but  when  the  con- 
centration reaches  3  parts  per  1000  sugar  appears 
in  the  urine.  The  sugar  content  increases  during 
digestion. 

Various  ferments  are  found  in  blood.  Among  them 
are  found  oxidizing  and  fat  splitting  ferments.  The 
presence  of  the  oxidizing  ferment  offers  a  very  delicate 
method  for  the  detection  of  blood.  Blood  as  dilute 
as  one  part  in  eighty  million  will  give  a  positive  peroxi- 
dase  test. 


232  THE  BLOOD 


SUMMAKY  OF   CHAPTER   XXXVIII. 

Blood  drawn  into  paraffined  tubes  will  not  clot 
immediately.  The  cellular  elements  may  be  removed, 
leaving  a  clear,  yellow,  alkaline  fluid  called  plasma. 
Plasma  clots  on  coming  into  contact  with  any  foreign 
body  it  can  "wet."  Blood  allowed  to  clot  carries  down 
the  cellular  elements  in  the  meshes  of  the  clot  leaving 
a  clear,  yellow,  alkaline,  sticky  liquid  called  serum. 
The  clotting  substance  is  fibrin.  It  may  be  obtained 
from  the  fresh  blood  by  whipping  with  wires.  The 
fibrin  sticks  to  the  wires. 

Fibrin  exists  in  the  blood  as  fibrinogen.  A  hypo- 
thetical substance  called  prothrombin  unites  with 
calcium  to  form  fibrin  ferment  which  in  turn  acts  on 
the  fibrinogen  to  produce  fibrin.  Calcium  is  essential 
to  the  clotting  of  blood  consequently  anything  which 
removes  the  calcium  as  sulphates  or  oxalates  prevents 
the  clotting  of  blood. 

Blood  serum  consists  of  a  colloidal  solution  of  globulin 
and  albumin  in  an  alkaline  solution  of  salts.  The  salts 
consist  mostly  of  NaCl,  MgCl2;  KC1  and  CaCl2  are 
also  present.  The  alkalinity  of  the  serum  is  due  to  the 
presence  of  alkali  carbonates  and  dihydrogen  phos- 
phates. Globulin  may  be  precipitated  by  removing 
the  salts  by  dialysis  or  half  saturation  writh  ammonium 
sulphate.  Albumin  may  be  precipitated  by  complete 
saturation  with  ammonium  sulphate.  The  ratio  of 
globulin  to  albumin  is  about  1  to  1.5.  Globulin  is 
also  precipitated  by  diluting  the  serum  and  passing  CO2 


SUMMARY  OF  CHAPTER  XXXVIII  233 

into  the  mixture.  Diphtheria  antitoxin  is  thus  con- 
centrated. 

The  red  cells  are  complex  in  their  composition. 
Besides  globulin,  lecithin,  etc.,  they  contain  hemoglobin, 
a  compound  proteid.  Hemoglobin  consists  of  simple 
proteids  plus  hematin,  the  red  coloring  matter  of  the 
blood.  Hemoglobin  unites  with  oxygen  in  the  lungs 
to  form  oxyhemoglobin  and  gives  up  the  oxygen  to 
the  various  cells  of  the  body  which  need  it. 

If  a  capsule  of  semipermeable  membrane  contain- 
ing salt  solution  is  placed  in  water,  the  water  passes 
into  the  salt  solution  through  the  wall.  This  is  called 
osmosis.  The  pressure  exerted  in  the  process  is  called 
osmotic  pressure.  Solutions  containing  equal  molec- 
ular concentrations  of  salts  and  exerting  the  same 
osmotic  pressure  are  said  to  be  isotonic.  More  dilute 
solutions  would  be  termed  hypotonic  and  more  con- 
centrated solutions  hypertonic.  A  solution  of  0.9 
per  cent.  NaCl  is  isotonic  with  the  red  cells  and  there- 
fore with  blood  serum.  More  dilute  solutions  burst 
(hemolyze  or  lake)  the  cell  and  the  coloring  matter  is 
dissolved  out.  Poisons  and  natural  substances  found 
in  blood,  also  substances  developed  after  the  repeated 
injection  of  washed  red  cells,  which  hemolyze  red 
cells,  are  called  hemolysins.  Monkey  serum  possesses 
a  strong  natural  hemolysin  for  sheep  corpuscles.  The 
serum  of  some  persons  will  hemolyze  the  red  cells  of 
others.  Therefore,  before  a  blood  transfusion,  the 
two  bloods  (of  the  donor  and  of  the  patient)  should  be 
tested  against  one  another  for  hemolysins. 


234  THE  BLOOD 

About  one-fourth  of  the  body  weight  is  blood.  The 
specific  gravity  of  blood  is  about  1056. 

Blood  carries  oxygen  to  the  body  cells  and  brings 
away  CO2.  It  also  furnishes  food  and  water  to  the 
cells  and  removes  their  waste  products.  Blood  also 
equalizes  the  temperature  of  the  body  and  maintains 
a  guard  over  the  various  parts.  When  local  injuries 
or  infections  occur  the  blood  transports  the  white 
cells  and  neutralizing  bodies  to  the  point. 

Dextrose  is  found  in  normal  blood '(1  to  1.5  parts 
per  1000). 

Ferments  of  various  kinds  are  also  found  in  normal 
blood. 


CHAPTER  XXXIX. 
MILK. 

MILK  is  an  albuminous  fluid  in  which  fat  is  emulsified 
and  the  protein  (casein)  is  held  in  colloidal  solution. 
If  one  adds  rennet  (a  ferment  taken  from  the  walls  of 
pig's  stomach)  to  milk,  it  clots.  The  casein  settles 
out  in  masses,  leaving  a  slightly  yellow,  clear  fluid 
above.  Acids  added  to  milk  produce  the  same  effect 
but  in  a  different  manner.  It  is  thought  that  the 
casein  is  held  in  colloidal  solution  by  calcium,  and  any 
substance  which  takes  away  the  calcium  allows  the 
casein  to  clot.  For  example,  hydrochloric  acid  added 
to  milk  unites  with  the  calcium,  taking  it  away  from 
the  casein.  Calcium  chloride  is  formed  and  casein  is 
precipitated.  The  clot  may  be  washed  and  shaken 
with  lime  water  to  reform  a  solution  of  casein.  The 
souring  of  milk  is  the  result  of  the  growth  of  acid- 
producing  microorganisms  in  it.  The  lactic  acid 
formed  by  the  fermentation  of  milk  sugar  (lactose) 
acts  in  the  same  manner  as  the  hydrochloric  acid 
referred  to  above. 

Casein. — Casein  is  a  compound  protein,  very  com- 
plex in  structure.  In  the  milk  it  is  said  to  exist  as 
caseinogen,  which  is  still  more  complex.  Caseinogen  is 
insoluble  in  water  and  so  is  calcium  phosphate,  but 


236  MILK 

together  they  form  a  colloidal  solution  which  gives  to 
milk  its  white  appearance. 

Besides  its  use  as  a  food,  casein  is  employed  exten- 
sively in  making  artificial  ivory.  Milk  is  the  only 
source  of  casein. 

Other  Proteins  in  Milk. — There  are  two  proteins  found 
in  milk  which  are  very  closely  related  to  those  found 
in  blood,  viz.:  lactalbumin  and  lactoglobulin.  Milk 
secreted  the  first  few  days  after  delivery  (colostrum) 
is  relatively  richer  in  these  two  proteins  than  normal. 
Human  milk  is  proportionally  richer  in  lactalbumin 
and  lactoglobulin  than  cow's  milk. 

Fats. — Milk  fats  are  emulsified  in  milk  but  on 
standing  the  globules  gradually  rise  on  account  of  the 
difference  in  specific  gravity.  Forcing  the  milk  through 
fine  holes  in  a  steel  plate  homogenizes  it  so  that  the 
cream  will  not  rise. 

When  milk  is  churned  the  violent  agitation  destroys 
the  emulsion  and  the  fat  globules  coalesce  to  form 
butter.  The  fat  globules  of  human  milk  are  smaller 
than  those  found  in  cow's  milk.  There  is  also  some 
difference  in  the  chemical  composition  (see  table). 

Milk  Sugar. — Milk  sugar,  lactose,  is  found  only  in 
milk.  It  is  composed  of  a  molecule  of  dextrose  and  a 
molecule  of  galactose.  Human  milk  contains  about  7 
per  cent.,  and  cow's  milk  about  5  per  cent.,  lactose. 

Salts. — The  salts  in  milk  are  very  similar  to  those 
found  in  the  blood.  The  kinds  and  relative  amount 
of  salts  determine  the  reaction  of  fresh  milk.  Human 
milk  is  more  alkaline  than  cow's  milk. 


HUMAN  AND  COW'S  MILK 


HUMAN  AND  COW'S  MILK. 


237 


Milk  from  every  source  is  similar  in  its  constituents, 
but  it  may  vary  greatly  in  different  species.  A  com- 
parison of  human  and  cow's  milk  is  given  in  the 
following  table:1 


Woman's  milk  direct 

Cow's  milk, 

from  the  breast. 

freshly  milked. 

Reaction. 

Amphoteric  (more  al- 

Amphoteric    (more     acid 

kaline  than  acid)  . 

than  alkaline). 

Water  

87  to  88  per  cent. 

86  to  87  per  cent. 

Mineral  matter    .      . 

0.20  per  cent. 

0  .  70  per  cent.  _ 

Totals  solids   .      .      . 

13  to  12  per  cent. 

14  to  13  per  cent. 

Fats     .     ..      .      .      .     , 

4.  00  per  cent,  (rela- 

3.50-4.00 per  ct.   (rela- 

tively poor  in  vola- 

tively   rich    in    volatile 

tile  glycerides). 

glycerides)  . 

Milk  sugar      .      .      . 

7.  00  per  cent. 

4  .  75  per  cent. 

Proteids     .      .  ;  .      . 

1  .  50  per  cent. 

3  .  50  per  cent. 

Caseinogen      .      .      . 

£  to  |  of  total  proteids. 

2.  66  per  cent. 

Whey  proteids      .      . 

|  to  3  of  total  proteids. 

0.84  per  cent. 

Coagulable  proteids  . 

Small  proportionally. 

Large  proportionally. 

Coagulation    of    pro- 

With    greater     diffi- 

With less  difficulty.  Curds 

teids  by  acids  and 

culty.  Curds  small 

large  and  tenacious. 

salts. 

and  flocculent. 

Coagulation    of    pro- 

Does   not    coagulate 

Coagulates  readily. 

teids  by  rennet. 

readily. 

Action  of  gastric  juice 

Proteids  precipitated 

Proteids  precipitated  but 

but  easily  dissolved 

dissolved  less  readily. 

in  excess  of  the  gas- 

trie  juice. 

Milk  as  a  Food. — It  has  been  said  that  milk  is  the 
ideal  food,  containing  as  it  does  all  three  classes  of 
foodstuffs,  carbohydrate,  fat,  and  protein.  It  will  be 
noted  that  while  milk  is  an  ideal  food  for  the  young 
and  growing  child,  it  is  not  a  balanced  ration  for 
older  children  or  adults.  It  has  far  too  much  protein 
and  contains  too  much  fat  in  proportion  to  the  amount 
of  sugar  present.  Furthermore,  it  is  not  sufficiently 

1  Quoted  from  Rotch:  Pediatrics. 


238  MILK 

concentrated.  In  order  to  obtain  a  normal  amount  of 
heat  for  the  metabolism  of  a  normal  man  during  one 
day,  it  can  be  calculated  that  over  four  quarts  of  milk 
would  be  necessary.  Milk  offers  a  very  convenient 
food  for  invalids  and  for  persons  requiring  such  protein 
diets,  and  skimmed  milk  is  one  of  the  cheapest  sources 
of  protein  for  the  normal  dietary.  Milk  is  the  most 
difficult  foodstuff  to.  produce  and  transport  in  a  hygienic 
manner.  All  sorts  of  microorganisms  flourish  in  it, 
and  several  diseases  have  been  known  to  have  been 
transmitted  in  epidemic  form  by  milk. 

SUMMARY  OF  CHAPTER  XXXIX. 

The  casein  of  milk  is  held  in  colloidal  solution  by 
calcium  phosphate.  In  milk  solution  it  exists  as  case- 
inogen,  which,  alone,  is  insoluble  in  water.  Calcium 
phosphate  is  also  insoluble,  but  caseinogen  and  calcium 
phosphate  together,  form  a  compound  which  goes 
into  colloidal  solution.  Obviously,  anything  which 
removes  the  calcium  from  this  combination  precipitates 
the  caseinogen  as  casein.  Acids  added  to  milk  unite 
with  the  calcium  and  the  casein  clots.  The  souring  of 
milk  is  the  result  of  the  growth  of  microorganisms  which 
produce  lactic  acid  from  the  milk  sugar.  Lactic  acid 
forms  calcium  lactate  and  the  casein  is  precipitated. 
Rennet,  a  ferment  found  in  the  wall  of  the  pig's 
stomach,  has  as  its  particular  function  the  clotting  of 
milk. 

Casein  is  a  complex  compound  protein.  2.66  per  cent, 
of  cow's  milk  or  0.75  per  cent,  of  human  milk  is  casein. 


SUMMARY  OF  CHAPTER  XXXIX  239 

The  clear  liquid  (whey)  resulting  from  filtering 
qlotted  milk  is  alkaline  in  reaction  and  contains  prac- 
tically the  same  inorganic  salts  as  blood  serum,  but  in 
different  proportions.  Whey  also  contains  lactalbumin 
and  lactoglobulin.  There  are  relatively  larger  amounts 
of  lactalbumin  and  lactoglobin  in  human  milk  than  in 
cow's  milk.  Colostrum  contains  far  greater  proportion 
of  these  two  proteids. 

The  fats  of  milk  are  emulsified  in  milk  but  on  standing 
rise  to  the  top  (cream).  About  4  per  cent,  of  normal 
milk  is  fat,  but  cow's  milk  often  contains  less.  The 
globules  in  cow's  milk  are  larger  and  there  are  chemical 
differences  between  the  fat  of  cow's  milk  and  that  of 
human  milk. 

Milk  sugar,  lactose,  is  composed  of  a  molecule  of 
dextrose  plus  a  molecule  of  galactose.  Lactose  is 
found  only  in  milk.  Human  milk  contains  about  7 
per  cent.,  and  cow's  milk  about  5  per  cent.,  lactose. 

Milk  contains  all  the  necessary  food  materials, 
namely,  protein,  fat,  sugar,  but  not  in  the  proportions 
required  by  adults.  Milk  is  the  ideal  food  for  babies, 
but  contains  too  much  protein  to  serve  as  an  exclusive 
diet  for  adults.  It  is,  however,  a  very  economical 
source  of  protein  for  the  dietary.  Milk  is  the  most 
difficult  foodstuff  to  produce  in  a  hygienic  manner. 


CHAPTER  XL. 
THE  URINE. 

URINE  is  a  solution  of  various  salts  and  certain 
organic  nitrogenous  bodies  in  water.  On  its  way 
through  the  urinary  passages  it  may  wash  down 
particles  consisting  of  debris  and  cells.  In  certain 
pathological  conditions  the  amount  of  matter  not  in 
solution  is  increased.  On  cooling,  certain  crystals 
may  be  deposited,  and  if  the  reaction  changes  a  visible 
precipitate  may  form. 

Amount. — The  amount  of  urine  excreted  varies 
very  considerably.  More  is  excreted  during  activity 
and  just  after  meals.  Coffee  and  tea  often  increase 
the  flow  temporarily.  Obviously  the  amount  of 
liquids  and  the  kind  and  amount  of  food  taken  affect 
the  volume  of  the  urine.  The  temperature  of  the  air 
and  humidity  have  very  marked  effects.  When  it  is 
hot,  and  both  sensible  and  insensible  perspiration 
are  increased,  the  urine  is  more  concentrated  than  on 
colder  days.  The  average  urine  output  varies  from 
800  to  1200  c.c.  for  the  average  man  in  twenty-four 
hours.  In  certain  diseases  the  urine  is  increased, 
while  in  other  disorders  the  reverse  is  true. 

Specific  Gravity. — Since  the  urine  contains  salts  and 
organic  bodies  in  solution,  the  specific  gravity  would  be 


ODOR  241 

expected  to  be  greater  than  1.  The  variation  in  volume 
under  normal  conditions  would  be  expected  to  cause 
some  variation  in  the  specific  gravity.  The  specific 
gravity  ordinarily  varies  between  1015  and  1025  (or 
1.015  to  1.025).  In  clinical  work  it  is  customary  to 
express  the  specific  gravity  of  water  as  1000,  and  of 
urine  in  terms  of  this  number.  After  excessive  per- 
spiration it  may  go  as  high  as  1040,  and  after  a  meal 
it  may  be  as  low  as  1010.  In  very  rare  instances  does 
it  go  below  1000 — probably  then  only  after  excessive 
amounts  of  alcohol  have  been  taken.  The  specific 
gravity  is  estimated  by  means  of  the  urinometer.  (See 
page  250.) 

Color. — Normal  urine  when  excreted  is  always  clear, 
but  it  has  a  distinct  color,  varying  from  a  pale  lemon 
yellow  to  deep  orange.  The  normal  yellow  color 
most  often  found  is  due  to  the  urine  pigment:  uro- 
chrome,  a  substance  whose  constitution  is  not  yet 
determined.  The  ingestion  of  drugs  and  vegetable 
coloring  matters  may  affect  the  color  of  the  urine. 
The  depth  of  color  will,  of  course,  depend  upon  con- 
centration and  vary  inversely  as  the  volume,  other 
things  being  equal.  In  pathological  conditions  bile 
or  blood,  etc.,  may  lend  color  to  the  urine. 

Odor. — Very  recently  it  has  been  claimed  that  the 
faint  aromatic  odor  of  fresh  urine  is  due  to  the  presence 
of  a  particular  substance  termed  uronoid.  Its  con- 
stitution has  not  been  determined.  After  the  ingestion 
of  asparagus  a  characteristic  odor  is  observed  due, 
it  is  claimed,  to  the  presence  of  a  methyl  mercap- 
tan  (a  sulphur-nitrogen-carbon  containing  organic 
16 


242  THE   URINE 

compound).  Other  vegetables  and  drugs  may  impart 
odor  to  the  urine.  Urine  decomposes  very  quickly 
and  its  odor  becomes  very  unpleasant.  Ammonia  is 
given  off  in  sufficient  quantities  to  be  detected  by  its 
odor. 

Reaction. — Normal  human  urine  is  usually  slightly 
acid  to  litmus,  due  to  the  presence  of  sodium  dihydrogen 
phosphate,  NaH2PO4.  Immediately  after  meals  when 
hydrochloric  acid  is  being  secreted  in  the  stomach 
the  urine  may  be  slightly  alkaline  because  the  HC1 
secreting  glands  extract  the  acid  radicals  from  the 
blood  for  the  time  being.  Organic  acids,  like  acetic 
(in  vinegar)  and  citric  (in  lemon  juice),  are  oxidized 
in  the  body  to  carbonates.  The  carbonates  are  ex- 
creted in  the  urine  and  consequently  increase  the 
alkalinity. 

On  standing,  fermentation  results  in  the  formation 
of  ammonia  and  the  urine  becomes  alkaline.  (See 
above.)  Alkaline  urine  becomes  cloudy  on  account 
of  the  precipitation  of  phosphates.  A  few  drops  of 
acetic  acid  will  clear  it  (i.  e.t  dissolve  the  phosphate). 
Alkaline  urine  may  deposit  small  crystals  of  ammonium 
urate  and  ammonium  magnesium  phosphates. 

Salts  of  the  Urine. — The  salt  occurring  in  the  urine 
in  largest  amounts  is  sodium  chloride.  The  actual 
amount  eliminated  from  day  to  day  depends  upon 
the  amount  ingested  upon  the  amount  excreted  in 
the  perspiration.  The  average  is  about  12  grams  per 
day.  Chlorides  of  potassium,  ammonium,  and  mag- 
nesium also  occur  in  the  urine.  The  phosphates  of 
urine  are  also  variable.  Phosphates  of  the  alkali 


ORGANIC  CONSTITUENTS  243 

metals  (Na  and  K),  of  the  alkaline  earths  (Ca  and  Mg), 
and  of  ammonium  are  found.  The  three  types  of  phos- 
phates may  be  represented  by  the  sodium  salt :  Normal 
phosphate,  Na3PO4;  monohydrogen,  Na2HPO4;  and 
the  dihydrogen  NaH2P04.  On  account  of  the  low 
solubility  of  phosphates  they  are  often  found  deposited 
as  microscopic  crystals  in  cold  urine.  The  sulphur 
of  the  urine  occur  as  inorganic  sulphates  and  also  in 
organic  combinations  (ethereal  sulphate  and  neutral 
sulphur  compounds).  Small  amounts  of  carbonates 
and  nitrates,  traces  of  fluorides  and  silicates,  and  some 
iron  are  also  found  in  urine  in  addition  to  the  salts 
already  enumerated. 

Organic  Constituents. — The  most  important  organic 
constituent  of  the  urine  is  urea.  About  90  per  cent, 
of  the  total  nitrogen  of  urine  is  urea.  An  average  of 
30  to  40  grams  of  urea  are  excreted  by  man  in  twenty- 
four  hours. 

If  nitric  acid  is  added  to  urine  and  the  mixture 
evaporated  to  one-third  volume  and  set  aside  to  cool 
crystals  resembling  six-sided  tiles  will  form.  These 
crystals  will  be  colored,  but  if  they  are  filtered  off, 
dissolved  in  water,  filtered  through  powdered  animal 
charcoal  and  concentrated  they  will  crystallize  with- 
out color. 

These  crystals  are  urea  nitrate.  If  BaC03  is  added 
to  a  solution  of  urea  nitrate,  CO2  is  given  off,  Ba(NO3)2 
is  formed  and  urea  is  set  free.  Urea  is  soluble  in  water 
but  insoluble  in  chloroform  or  ether.  It  crystallizes 
in  colorless,  long,  six-sided  prisms. 


244  THE   URINE 

Urea  has  the  composition 

NH2 

c=o. 

I 

NH2 

It  can  be  made  synthetically  by  heating  ammonium 
carbonate.  The  first  step  is  the  driving  off  of  1  mole- 
cule of  water  forming  ammonium  carbamate: 

O.NH4  NH2 

=O    +   H2O. 


Continued  heating  changes  ammonium  carbamate  in 
the  same  manner. 

NH2  NH2 

I  I 

C=O >  C=O  +  H2O. 

I  I 

O.NH4  NH2 

Urea. 

Urea  is  decomposed  by  HN02  (nitrous  acid)  into 
gaseous  nitrogen  and  CO2.  The  CO2  can  be  absorbed 
by  NaOH  and  the  amount  of  N  gas  measured.  The 
amount  of  urea  can  then  be  calculated.  (See  chapter 
on  Uranalysis.) 

It  has  been  stated  (see  proteins)  that  proteins  are 
broken  down  during  digestion  into  amino-acids.  The 
amino-acids  are  absorbed  and  at  some  unknown  place 
are  reassembled  to  form  proteins  when  they  are  neces- 
sary for  growth  or  repair.  Excess  of  proteins  are  not 
stored  in  the  body  as  fat  and  sugars  are.  The  excess 
of  amino-acids  are  oxidized  in  the  liver  to  form  urea  and 


ORGANIC  CONSTITUENTS  245 

excreted  in  the  urine.  Therefore  the  amount  of  urea 
in  the  urine  varies  with  the  amount  of  proteins  ingested. 
Urea  is  also  excreted  in  the  sweat. 

Uric  ^4cid.—  Although  the  actual  amount  of  uric 
acid  excreted  in  twenty-four  hours  is  comparatively 
small  (about  0.5  gram)  it  is  considered  an  important 
constituent  of  the  urine.  It  is  supposed  to  come  from 
the  breaking  down  of  the  nuclei  of  body  cells  and 
from  the  nuclei  of  cells  in  the  meat  ingested. 

The  crystals  of  uric  acid  may  assume  several  forms: 
like  wedges,  prisms,  plates,  or  dumb  bells.  Free  uric 
acid  is  insoluble  in  water  but  its  lithium  and  its  sodium 
salts  are  easily  soluble.  Ammonium  urate  is  very 
slightly  soluble.  Crystals  of  uric  acid  or  ammonium 
urate  are  colorless  when  pure,  but  they  occlude  coloring 
matters  so  that  often  the  brownish-red  precipitate 
seen  in  urines,  after  standing,  consists  of  uric  crystals 
or  its  salts.  Uric  acid  in  excess  reduces  Fehling's 
solution  slightly,  and  may,  therefore,  when  present 
in  large  amounts,  interfere  with  sugar  tests  in  the 
urine.  The  formula  for  uric  acid  is: 


HN  — 

O=C  -  C—  NH 

CO. 
HN  —  C  —  NH 

It  is  a  tri-oxy-purine.  On  oxidation  the  three  C 
atoms  connected  with  one  another  are  changed  to  CO2 
and  two  molecules  of  urea  are  given  off. 

Indican.  —  Indoxyl  potassium  sulphate  or  indican 
is  one  of  the  most  important  of  the  ethereal  sulphuric 


246  THE   URINE 

acids  found  in  the  urine.  It  is  oxidized  by  chlorine 
(bleaching  powder)  to  indican  blue  or  indican  red. 
(See  test  for  Indican  in  Appendix.)  Indican  is  a  product 
of  putrefaction  and  when  found  in  the  urine  is  evidence 
that  putrefaction  is  taking  place  in  the  intestinal 
contents. 

Creatinin  seems  to  be  a  product  of  cell  activity,  and 
on  a  creatin-free  diet  the  amount  excreted  seems  to  be 
fixed  for  each  individual.  Creatin  occurs  in  muscle: 
creatinin  is  reduced  creatin.  For  formula  and  prop- 
erties, refer  to  any  text-book  on  physiological 
chemistry. 

Other  Organic  Constituents  of  the  Urine. — A  greaf. 
many  other  organic  compounds  of  more  or  less  com- 
plexity may  occur  in  variable  quantities.  Their 
presence  in  small  quantities  may  be  normal,  but  the 
extent  to  which  they  may  be  present  to  constitute 
abnormality  varies  under  different  conditions. 


SUMMARY  OF  CHAPTER  XL. 

The  amount  of  urine  excreted  varies  markedly. 
The  temperature  and  humidity,  the  amount  of  water 
drunk,  the  kind  and  quantity  of  food  ingested,  and 
the  blood-pressure  affect  the  secretion  of  urine.  The 
average  varies  from  800  to  1200  c.c.  per  day. 

The  specific  gravity  varies  with  the  volume  and  with 
diseased  conditions.  It  generally  varies  from  1015 
to  1025,  though  it  may  exceed  these  limits  under 
certain  conditions  and  still  be  normal.  Under  normal 
conditions,  urine  of  high  specific  gravity  makes  us 


SUMMARY  OF  CHAPTER  XL  247 

suspicious  of  diabetes  and  tests  for  sugar  in  urine  are 
accordingly  made. 

The  color  is  also  subject  to  considerable  variation 
from  pale  yellow  to  deep  orange.  The  normal  color 
is  due  to  urochrome.  Bile  salts  are  found  in  abnormal 
conditions.  Substances  taken  into  the  stomach  may 
be  eliminated  in  the  urine  and  change  its  color. 

The  odor  of  the  urine  is  said  to  be  due  to  a  substance 
of  unknown  composition  called  uronoid.  Substances 
in  the  food  may  impart  a  characteristic  odor  to  the 
urine,  e.  g.,  asparagus. 

The  reaction  of  fresh,  normal,  human  urine  is  slightly 
acid,  although  after  the  ingestion  of  large  amounts  of 
vegetables  or  organic  acids  it  may  be  alkaline.  De- 
composition of  various  nitrogenous  bodies  in  the  urine 
by  ferment  action  soon  renders  the  urine  alkaline. 
This  alkalinity  results  from  the  ammonia  liberated. 

The  salts  of  the  urine  consist  mainly  of  NaCl.  About 
12  grams  of  NaCl  per  day  are  excreted.  Chlorides  of 
K,  (NH4),  Mg,  and  Ca  are  also  found.  Phosphates 
of  alkaline  metals  and  alkaline  earths  occur.  The 
three  types  of  phosphates  found  may  be  represented 
as  follows:  (1)  M3PO4;  (2)  M2HPO4;  and  (3)  MH2PO4, 
in  which  M  represents  any  monovalent  metal  like  Na 
or  K.  Sulphates  (inorganic  and  organic)  and  small 
amounts  of  carbonates  and  nitrates  are  found. 

The  most  important  organic  constituent  is  urea. 
90  per  cent,  of  the  total  N  is  urea  N.  30  to  40  grams 
of  urea  are  excreted  by  an  average  man  in  one  day. 
Urea  can  be  separated  from  urine  by  adding  HNO3. 
The  urea  nitrate  can  be  recrystallized  and  finally 
decomposed  by  BaCO3.  Urea  has  the  composition 


248  THE  URINE 

CO(NH2)2.  It  can  be  made  synthetically  by  heat- 
ing ammonium  carbonate.  Ammonium  carbamate 
CO.NH2.O.NH4  is  first  formed  and  later  changes  to 
urea  on  losing  1  molecule  H2O.  Urea  is  formed  in  the 
liver  by  the  oxidation  of  the  groups  of  amino-acids 
which  have  not  been  utilized  to  rebuild  proteins. 

Urea  is  decomposed  by  HN02  forming  gaseous 
nitrogen  and  C02. 

Uric  acid  is  supposed  to  result  from  the  breaking 
down  of  the  nuclei  of  ingested  cell  nuclei.  On  standing, 
urine  deposits  crystals  of  urine  acid,  especially  after 
the  urine  becomes  alkaline.  Uric  acid  forms  salts  with 
Na,  K,  and  (NH4)  groups.  Sodium  and  potassium 
urates  are  much  more  soluble  in  water  than  ammonium 
urate.  Uric  acid  in  excess  reduces  Fehling's  solution 
and  may  thus  be  a  source  of  error  in  examining  a 
sample  of  urine  for  sugar.  Uric  acid  is  a  tri-oxy-purine 
(closely  related  to  the  alkaloid  caffeine).  Urea  is 
formed  by  the  oxidation  of  uric  acid. 

Indican  is  indoxyl  potassium  sulphate.  When  this 
body  is  found  in  urine  it  indicates  intestinal  putrefac- 
tion. It  may  be  detected  in  urine  containing  it  by 
treating  with  bleaching  powder.  A  blue  or  red  color 
indicates  the  presence  of  indican. 

Creatinin  seems  to  be  a  product  of  cell  activity,  and 
on  a  creatin-free  diet  the  urine  of  individuals  contains 
a  fairly  constant  amount  of  creatinin  peculiar  to  that 
person.  Creatin  occurs  in  muscle:  creatinin  is  reduced 
creatin. 

Other  organic  compounds  may  be  found  at  times  in 
the  urine,  but  are  of  interest  more  to  the  students  of 
physiological  and  pathological  chemistry. 


CHAPTER  XL1. 
URANALYSIS. 

THE  normal  appearance  of  a  sample  of  urine  is  no 
guarantee  that  it  is  normal.  It  is  very  important 
that  specimens  should  be  tested,  even  though  they 
appear  to  be  perfectly  normal. 

Collection  of  the  Urine. — For  chemical  analysis  of 
urine  it  is  extremely  important  that  a  well-mixed 
twenty-four-hour  specimen  be  collected,  for  the  reason 
that  the  character  of  the  various  voidings  are  subject 
to  wide  variations. 

Sometimes  it  is  desired  that  the  night  urine  be  kept 
separate.  In  this  case  the  voidings  between  9  P.M. 
and  6  A.M.  are  poured  together.  A  twenty-four-hour 
specimen  includes  voidings  beginning  with  the  first 
after  6  A.M.  and  including  the  6  A.M.  voiding  on  the 
next  day.  It  is  very  essential  that  all  voidings  should 
be  saved  and  the  total  accurately  measured. 

Preservation  of  Urine. — All  specimens  should  be  kept 
in  the  ice-box  until  immediately  before  examination. 
Urine  is  easily  fermented — the  reaction  changes, 
urea  is  decomposed,  the  ammonia  content  increases, 
carbohydrates  may  be  fermented,  and  the  microscopic 
elements  decompose  if  the  specimen  is  not  kept  cold. 

Various  preservatives  have  been  recommended  for 


250  .        URANALYSIS 

special  kinds  of  work.  The  analyst  should  know  the 
preservation  used.  For  chemical  work  chloroform  is 
perhaps  the  best.  Add  5  c.c.  for  each  liter  of  urine. 
The  urine  should  be  well  shaken  after  each  addition 
and  the  bottle  kept  tightly  corked.  The  chloroform 
settles  to  the  bottom  and  adds  nothing  to  the  volume. 
Immediately  before  analysis  the  urine  may  be  poured 
off  the  chloroform  and  a  sample  exposed  to  incubator 
temperature  for  a  very  few  minutes,  or  air  bubbled 
through  in  order  to  remove  traces  of  chloroform.  Any 
larger  trace  of  chloroform  may  yield  a  suggestive 
reducing  reaction  with  Fehling's  solution.1  If  formalin 
is  used  one  is  more  liable  to  obtain  suggestive  sugar 
reactions  with  Fehling's  solution,  yet  for  microscopic 
examination  formalin  seems  the  best  preservative. 
Thymol  is  used  sometimes,  but  a  test  similar  to  bile 
may  be  obtained  in  the  specimen. 

Amount  of  Urine. — The  amount  of  urine  should  be 
carefully  measured  in  a  cylinder  registering  volume 
in  cubic  centimeters. 

Specific  Gravity. — For  clinical  examination  the  specific 
gravity  is  approximated  by  using  the  urinometer.  The 
instrument  is  standardized  to  read  1000  in  distilled 
water  at  15°  C. 

The  glass  cylinder  should  be  clean  and  dry.  It  is 
filled  about  four-fifths  full  of  urine  by  gently  pouring 
in  order  to  prevent  foaming.  Foam  should  be  re- 
moved with  a  strip  of  filter  paper. 


1  Formalin  does  not   reduce   Benedict's    solution    but   chloroform 
does.     For  each  liter  of  urine  2.5  c.c.  formalin  is  sufficient. 


COLOR  251 

The  temperature  is  important.  A  small  thermometer 
should  be  placed  in  the  urine  and  stirred  a  few  times. 
If  the  temperature  is  not  15°  C.  the  jar  should  be 
placed  in  warm  or  cool  water,  as  the  case  requires, 
and  gently  stirred  until  the  thermometer  registers 
15°.  If  the  proper  temperature  cannot  be  attained 
in  a  hurried  examination,  a  correction  by  adding  for 
every  3°  above  15°  is  made.  For  example,  a  urine 
reading  1022  at  21°  should  be  corrected  to  read 
1024. 

The  bobbin  should  be  clean  and  dry.  It  is  inserted 
carefully  and  gently  tapped  and  read  when  it  comes 
to  rest.  It  is  important  that  the  bobbin  does  not  touch 
the  side  or  bottom  of  the  cylinder.  The  graduation 
on  level  with  the  surface  of  the  urine  (the  bottom  of 
the  meniscus)  is  read  and  recorded. 

In  a  child's  or  catheterized  specimen  there  may 
not  be  sufficient  urine  to  fill  the  cylinder.  Dilute  with 
equal  parts  of  water  and  test  as  above.  Multiply 
the  last  two  figures  by  2  and  add  to  1000.  If  reading 
is  1010,  then  10  X  2  =  20;  20  +  1000  =  1020  (correct 
reading) . 

Total  Solids. — When  requested,  estimate  total  soMds 
by  multiplying  the  last  two  figures  of  the  specific 
gravity  by  Haser's  empirical  coefficient  2.33.  This  will 
give  grams  per  liter.  To  find  percentage  divide  by  10. 

Color. — The  color  of  a  given  depth  of  urine  viewed 
against  a  white  background  is  recorded  in  well-recog- 
nized terms :  straw,  light  yellow,  yellow,  amber,  orange, 
brown,  brownish  red,  etc.  If  the  foam  is  yellow, 
bile  is  present.  The  foam  is  otherwise  white. 


252  UR ANALYSIS 

The  character  of  any  precipitate  is  described  as  to 
amount  (small,  moderate,  abundant),  color,  and  con- 
sistency (dense  or  flocculent).  The  general  appearance 
of  the  urine  (clear,  cloudy)  is  observed. 

Odor. — A  small  amount  of  urine  is  brought  to  boiling 
in  a  beaker  covered  with  a  watch-glass.  The  glass  is 
removed  and  odor  recorded  as  fruity,  ammoniacal, 
sulphidic,  etc. 

Reaction. — A  strip  of  blue  and  of  red  litmus  paper 
are  immersed  to  half  their  length  in  the  urine  and 
immediately  withdrawn.  The  color  change  is  observed. 
If  the  blue  paper  changes  quickly  to  red,  the  urine  is 
strongly  acid;  a  slight  change  is  interpreted  as  faintly 
acid.  The  strips  are  laid  on  white,  clean,  dry  filter 
paper.  If  the  red  paper  changes  blue,  the  urine  is 
recorded  as  being  alkaline.  If  the  strip  of  litmus  is 
allowed  to  dry  and  becomes  red  again,  the  alkalinity 
is  recorded  as  being  due  to  ammonia,  otherwise  it  is 
due  to  a  fixed  alkali.  Normal  urine  is  always  faintly 
acid,  varying  with  the  diet. 

Total  Acidity. — When  required,  the  total  acidity 
may  be  determined  by  titrating  with  yV  NaOH,  accord- 
ing to  the  method  of  Folin. 

25  c.c.  of  urine  are  delivered  from  a  pipette  into  a 
200  c.c.  Erlenmeyer  flask.  100  c.c.  distilled  water, 
20  grams  potassium  oxalate,  and  2  drops  of  a  0.5  per 
cent,  alcoholic  solution  of  phenolphthalein  are  added. 
The  flask  is  shaken  well  for  one  minute  and  -£$  NaOH 
added  from  a  burette  until  a  distinct  reddish  color 
is  produced.  The  flask  is  shaken  after  each  addition. 
The  amount  of  NaOH  necessary  to  produce  color  when 


REDUCING  SUGARS  253 

multiplied  by  4  gives  the  number  of  c.c.  •£$  alkali 
required  per  100  c.c.  urine. 

Albumin. — Albumin  is  coagulated  and  precipitated 
by  heat.  Pour  into  a  clean  chemical  test-tube  2  c.c. 
of  a  saturated  solution  of  NaCl  in  water.  Pour 
in  filtered,  clear,  slightly  acid  urine  until  three- 
quarters  full.  The  top  zone  of  f  to  1  inch  is  heated 
to  boiling  in  a  small  flame  (alcohol  lamp  preferred). 
If  a  whitish  cloud  is  observed  in  the  heated  zone, 
when  viewed  against  a  black  background,  add  one 
drop  of  25  per  cent,  acetic  acid  and  boil  again.  Repeat 
the  addition  of  acetic  acid  and  the  boiling  three  times. 
If  the  precipitate  is  due  to  phosphates  this  treatment 
will  cause  it  to  disappear.  If  the  cloudiness  is  due 
to  albumin  it  will  persist  and  perhaps  increase.  The 
whitish  deposit  sometimes  formed  on  the  glass  by  the 
flame,  especially  when  gas  is  used,  should  not  be  con- 
fused with  an  albumin  test.  If  much  albumin  is 
present  a  heavy  flocculent  precipitate  will  be  formed. 

Heller's  Nitric  Acid  Test. — Place  10  c.c.  of  clear, 
concentrated  nitric  acid  in  a  two-ounce  conical  stand 
glass.  (If  the  nitric  acid  is  yellow,  boil  in  a  beaker 
until  clear.)  With  a  pipette  carefully  overlay  about 
25  c.c.  filtered  urine  over  the  nitric  acid.  After  three 
minutes  observe  the  line  of  contact  against  a  dark 
background.  A  precipitate  at  the  juncture  of  the  two 
liquids  indicates  albumin.  The  red  or  reddish-violet 
ring  often  observed  should  not  be  mistaken  for  a 
precipitate. 

Reducing  Sugars. — Fehling's  Method. — Solution  A. 
—Dissolve  34.65  grams  powdered  CuSCX  in  300  c.c. 
warm,  distilled  water  in  a  500  c.c.  volumetric  flask. 


254  UR ANALYSIS 

Allow  to  cool  and  make  up  to  mark  (500  c.c.)  with 
cold,  distilled  water. 

Solution  B. — Weigh  out  roughly  on  filter  paper 
125  grams  potassium  hydroxide.  (KOH  is  caustic; 
handle  with  forceps.  Break  sticks  in  a  large  mortar.) 
Place  in  a  500  c.c.  beaker  and  add  300  c.c.  distilled 
\vater.  When  all  is  dissolved  pour  into  a  500  c.c. 
volumetric  flask  and  rinse  three  times  with  small  por- 
tions of  distilled  water,  pouring  each  portion  into  the 
flask.  Pulverize  about  180  grams  sodium-potassium 
tartrate  (Rochelle  salt)  in  a  mortar.  Weigh  out  exactly 
on  glazed  paper  173  grams  of  powdered  Rochelle  salt 
and  pour  carefully  into  flask  containing  the  KOH 
solution.  Shake  until  all  is  dissolved;  allow  to  cool 
and  make  up  to  500  c.c.  mark  with  distilled  water; 
preserve  in  a  rubber-stoppered  bottle. 

For  tests,  mix  equal  parts  of  solutions  A  and  B 
immediately  before  using.  To  1  c.c.  of  the  mixture  in 
a  test-tube  add  4  c.c.  distilled  water  and  boil.  (If  a 
precipitate  is  formed  the  solutions  are  worthless.) 
To  the  warm  solution  add  three  or  four  drops  of  the 
urine  to  be  tested  and  boil.  Repeat  this  several  times. 
A  yellow  or  brownish  precipitate  indicates  the  presence 
of  reducing  sugars.  Phosphates  and  uric  acid  may  form 
precipitates  which  may  be  confused  with  the  positive 
reaction.  Fehling's  solution  should  not  be  used  after 
it  has  stood  over  long  periods. 

Benedict's  Method. — Dissolve  173  grams  sodium 
citrate  and  100  grams  anhydrous  sodium  carbonate 
in  600  c.c.  distilled  water.  Pour  through  a  folded  filter 
into  a  glass  graduate  and  make  up  to  850  c.c.  with 


PROCEDURE  255 

water.  Dissolve  17.3  grams  powdered  copper  sulphate  in 
100  c.c.  water  and  make  up  to  150  c.c.  with  water.  Place 
solution  1  (carbonate-citrate  solution)  in  a  large  beaker 
and  add  the  copper  solution  slowly  with  constant  stir- 
ring. The  mixed  solution  is  stored  in  a  rubber-stoppered 
bottle.  It  does  not  deteriorate  on  long  standing. 

Procedure. — To  500  of  Benedict's  solution,  in  a 
test-tube,  add  eight  drops  of  the  urine  to  be  tested 
and  boil  for  three  minutes.  Allow  to  cool  spontane- 
ously (do  not  cool  under  tap).  If  glucose  is  present 
a  large  precipitate  will  form,  otherwise  the  solution 
will  remain  perfectly  clear  or  only  slightly  turbid. 

Quantitative  Estimation  of  Dextrose. — Benedict's 
Method. — Benedict's  quantitative  solution  is  made  up 
as  follows:  Dissolve  in  750  c.c.  hot  distilled  water  the 
following:  crystals  of  sodium  carbonate,  200  grams 
(or  anhydrous  100);  sodium  or  potassium  citrate  200 
grams,  and  125  grains  potassium  sulphocyanate.  When 
all  is  dissolved  filter  if  the  solution  is  not  clear. 

Dissolve  exactly  18  grams  pulverized,  pure  crystals 
of  copper  sulphate  in  100  c.c.  water  and  pour  slowly 
into  solution  No.  1,  with  constant  stirring.  Allow  to 
cool,  add  5  c.c.  of  a  5  per  cent,  aqueous  solution  of 
potassium  ferrocyanide  solution  and  make  up  to 
1000  c.c.  with  distilled  water.  This  solution  keeps 
indefinitely  in  a  rubber-stoppered  bottle. 

Procedure. — If  the  urine1  to  be  titrated  shows  very 
heavy  reduction  (i.  e.,  contains  probably  a  large  amount 

1  In  case  chloroform  was  used  for  preservation,  a  portion  of  the 
urine  should  be  brought  to  boiling-point  and  quickly  cooled.  This 
rids  it  of  the  chloroform. 


256  URANALYSIS 

of  sugar)  dilute  10  c.c.  of  it  to  100  c.c.  with  distilled 
water.  Fill  a  clean  and  dry  50  c.c.  burette  with  the 
solution. 

Exactly  25  c.c.  of  Benedict's  solution  is  measured 
with  a  pipette  into  a  porcelain  evaporating  dish, 
25  cm.  in  diameter,  and  to  it  about  15  grams  of  crystal- 
lized sodium  carbonate  (or  8  grams  dry  Na2COs)  are 
added.  Half  a  teaspoonful  of  powdered  pumice  or 
talc  is  added  and  the  dish  heated  to  boiling  over  a 
free  flame  until  the  carbonate  has  entirely  dissolved. 

The  diluted  urine  is  now  run  from  the  burette 
rather  rapidly  until  a  chalk-white  precipitate  forms, 
and  the  blue  color  of  the  mixture  begins  to  lessen 
perceptibly.  Now  the  diluted  urine  must  be  dropped 
from  the  burette  very  slowly — a  few  drops  at  a  time — 
until  the  disappearance  of  the  last  trace  of  blue  color 
which  marks  the  end-point.  The  solution  must  be 
kept  boiling  vigorously  throughout  the  entire  titration. 
If  the  boiling  mixture  begins  to  bump  or  spatter  add 
a  little  distilled  water  to  make  up  for  the  loss  by 
evaporation. 

Calculation. — The  amount  of  diluted  urine  which  was 
necessary  to  reach  the  end-point  is  found  by  reading 
the  burette.  This  figure  divided  by  10  gives  the 
equivalent  amount  of  urine  (because  the  burette  con- 
tained urine  diluted  ten  times).  This  amount  of  urine 
must  contain  50  mg.  (0.05  gram)  of  dextrose,  because 
it  requires  50  mg.  dextrose  to  reduce  25  c.c.  Benedict's 
solution. 

Let  x  =  amount  of  urine  containing  50  mg.  dextrose, 
then  ^  x  100  =  per  cent,  sugar  in  original  urine. 


UREASE  METHOD  257 

Urea. — Hypobromite  Method.1 — Solution  A. — Dissolve 
62.5  grams  sodium  bromide  in  400  c.c.  water.  Pour 
into  a  500  c.c.  volumetric  flask.  Add  22  c.c.  pure 
bromine  (under  hood — bromine  fumes  are  very  irritat- 
ing), and  make  up  to  500  c.c.  with  distilled  water. 
Preserve  in  rubber-stoppered  bottles. 

Solution  B. — Dissolve  125  grams  sodium  hydroxide 
in  400  c.c.  distilled  water.  Allow  to  cool.  Pour  into 
a  volumetric  flask  and  make  up  to  500  c.c.  Preserve 
in  a  rubber-stoppered  bottle. 

Into  the  open  arm  of  the  clean  Doremus-Hinds 
ureometer  add  a  drop  or  two  of  urine;  turn  the  stop- 
cock so  that  the  urine  just  fills  the  lumen  and  turn  to 
off  position.  Fill  the  closed  arm  with  a  mixture  of 
equal  parts  of  solutions  A  and  B,  and  tilt  to  let  out 
any  air.  Set  upright  and  fill  open  arm  with  urine, 
avoiding  bubbles  of  air.  Turn  stop-cock  and  allow 
1  c.c.  urine  to  flow  in.  After  twenty  minutes  read  the 
amount  of  gas  in  the  closed  arm.  Each  small  sub- 
division of  gas  represents  0.001  gram  of  urea  per  cubic 
centimeter  of  urine.  If  percentage  is  desired  move  the 
decimal  point  two  places  to  the  right.  Every  small 
division  means  0.1  per  cent.  urea. 

Urease  Method. — Van  Slyke's  Modification  of  Mar- 
shall's Method. — This  method  is  accurate  and  so  simple 
that  the  nurse  with  little  laboratory  experience  can  be 


1  The  following  method  for  the  preparation  of  the  hypobromite 
solution  has  also  been  recommended.  Keep  on  hand  in  a  rubber- 
stoppered  bottle  a  20  per  cent,  solution  of  NaOH.  When  ready  for 
a  test  add  to  40  c.c.  of  this  solution  1  c.c.  of  pure  bromine  and  shake. 
This  solution  may  be  used  in  place  of  the  mixture  of  A  and  B,  as 
indicated  in  the  text. 
17 


258  UR ANALYSIS 

taught  to  use  it.  The  determinations,  especially  the 
first,  should  be  done  under  the  direction  of  a  physio- 
logical chemist.  The  details  of  the  method  are  given 
for  reference  of  the  nurse  after  she  has  learned  to  apply 
it.  The  method  depends  upon  the  fact  that  urease,  a 
ferment  found  in  the  soy  bean,  is  capable  of  convert- 
ing urea  into  ammonia  without  any  loss  of  nitrogen. 
The  ammonia  can  then  be  blown  out  of  the  urine  into 
a  known  amount  of  standard  acid.  The  acid  is  titrated 
at  the  end  of  the  experiment  to  determine  how  much 
has  been  neutralized  by  the  ammonia. 

The  method  is  rapid  and  of  advantage  on  account 
of  the  fact  that  several  analyses  may  be  run  at  the  same 
time. 

PROCEDURE. — One-half  c.c.  of  urine1  is  measured 
into  the  bottom  of  tube  A.  Exactly  5  c.c.  of  a 
solution  containing  6  grams  of  KH2P04  per  liter  are 
then  run  in  from  a  burette,  and  1  c.c.,  accurately 
measured,  of  a  10  per  cent,  solution  of  urease2  is  added. 

1  An  Ostwald  pipette  is  used,  the  stem  of  which  is  a  heavy  walled 
capillary  tube  of  only  1  mm.  bore.     The  pipette,  which  should  deliver 
in  about  twenty  seconds,  is  calibrated  by  weight  for  blow-out  delivery, 
and  permits  measurement  with  an  accuracy  of  0.001  c.c.    The  pipette 
is  allowed  to  deliver  with  its  tip  against  the  lower  part  of  the  test-tube 
wall  until  the  bulb  is  emptied;  the  remainder  of  the  contents  is  then 
blown  out. 

These  pipettes,  as  well  as  the  100  c.c.  test-tubes  of  special  heavy 
glass,  provided  with  inlet  and  outlet  for  aeration,  the  block  holder 
shown  in  the  figure,  and  a  brass  aspirator  pump  suitable  for  the  method 
can  be  obtained  from  Emil  Greiner,  45  Cliff  Street,  New  York. 

2  The  enzyme  preparation  used  should  be  standardized  as  follows: 
A  solution  is  made  containing  3  grams,  accurately  weighed,  of  pure 
urea  per  100  c.c.     Using  the  special  pipette  described  in  the  urine 
analysis,  one  measures  into  tube  A,  0.5  c.c.  of  the  above  urea  solution, 
5  c.c.  of  0.6  per  cent.  KH2PO4,  and  the  amount  of  enzyme  solution 
intended  to  be  used  in  analysis  (usually  1  c.c.  of  10  per  cent,  enzyme). 
The  reaction  is  allowed  to  run  at  room  temperature  (or  50°  if  desired) 


UREASE  METHOD  259 

The  solutions  in  the  tube  are  well  mixed,  2  drops  of 
caprylic  alcohol  to  prevent  subsequent  foaming  are 
added,  and  the  stopper  bearing  the  aerating  tubes 
shown  in  the  figure  is  put  into  place.  Twenty  minutes 
at  a  room  temperature  of  15°,  or  fifteen  minutes  at 
20°  or  above,  are  allowed  for  complete  decomposition 
of  urea.  No  harm  is  done  if  the  solutions  are  allowed 
to  stand  longer,  but  the  time  must  not  be  cut  shorter 
unless  more  enzyme  is  used.  While  the  enzyme  is 
acting,  one  measures  25  c.c.  of  -^  hydrochloric  or 
sulphuric  acid  into  tube  B  and  connects  the  tubes  as 
shown  in  the  figure.  After  the  time  for  complete 
decomposition  of  urea  has  elapsed  the  air  current  is 
passed  for  a  half  minute  in  order  to  sweep  over  into  B 
a  small  amount  of  ammonia  which  has  escaped  into 
the  air  space  of  A  during  the  decomposition.  A  is 
now  opened  and  4  to  5  grams  of  potassium  carbonate 
measured  roughly  from  a  spoon  are  poured  in  (in  order 
to  assure  most  rapid  removal  of  ammonia  by  air 
current  it  is  necessary  to  have  the  solution  at  least 
half  saturated  with  carbonate).  The  air  current  is 
now  passed  rapidly  through  the  tubes  until  all  the 
ammonia  has  been  driven  over  into  the  acid  in  B. 
The  time  required  for  this  depends  on  the  speed  of 

for  the  length  of  time  allowed  in  analysis,  and  the  ammonia  is  deter- 
mined as  described  for  urine  analyses.  It  should  neutralize  25  c.c. 
of  -^  acid.  If  it  falls  slightly  short,  it  is  well  to  repeat  the  test, 
doubling  the  time  interval,  as  some  samples  of  urea  are  not  100  per 
cent,  pure,  and  the  short  figure  may  be  the  fault  of  the  urea,  not  of 
the  enzyme.  If  in  the  longer  interval  no  more  ammonia  is  formed 
than  in  the  shorter,  the  urea  decomposition  was  complete  in  the  shorter 
time,  and  the  enzyme  is  sufficiently  active.  This  method  is  described 
in  detail  in  the  article  by  Van  Slyke  and  Cullen,  Journal  Biological 
Chemistry,  vol.  xix,  No.  2,  October,  1914. 


260 


UR ANALYSIS 


the  air  current.    With  a  rapid  pump  or  house  vacuum 
it  is  possible  to  aerate  completely  in  five  minutes; 


Tb  Pump 


-Wash  Bottle 


Apparatus  for  determining  urea  content  by  means  of  urease. 
(Journal  of  Biological  Chemistry.) 


while  a  slow  pump  may  require  a  half  hour.    The  time 
required  for  complete  aeration  is  determined  for  the 


BILE  261 

particular  vacuum  used  by  trial,  and  a  safe  margin 
allowed  in  the  determinations.  When  the  aeration  is 
finished  the  excess  acid  in  B  is  titrated  with  ^  NaOH. 
The  operations  can  be  concisely  summarized  in  the 
following  diagrammatic  form: 

0.5  c.c.  urine. 

,     ,,  .   ,  5.0  c.c.  0.6  per  cent.  KH2P04. 

1.  Measure  into  A      .  1Q  ^   1Q  pPer  ^  urease> 

2  drops  caprylic  alcohol. 
Place  stopper  as  shown  in  Fig.  1  and  let  stand  fifteen  minutes. 

{25  c.c.  5nc  acid. 
1  tUZ^i^.8*1" 
1  drop  caprylic  alcohol. 

3.  (After  15  minutes  standing)  aerate  one-half  minute.     Then  open 
A  and  add  4  to  5  grams  K^COs. 

4.  Aerate  all  NHs  from  A  over  into  B. 

5.  Titrate  excess  acid  in  B  with  ^  NaOH. 

6.  Calculate:     0.056  X  c.c.    J^    acid  =  grams    urea  +  ammonia 
nitrogen  per  100  c.c.  urine. 

In  order  to  determine  the  ammonia  nitrogen  alone 
one  measures  5  c.c.  of  urine  into  A,  adds  the  carbonate 
at  once,  and  aerates  as  described  above.  The  acid 
neutralized  is  multiplied  in  this  case  by  the  factor 
0.0056,  to  give  the  per  cent,  of  ammonia  nitrogen. 
No  extra  time  is  required  for  the  ammonia  determina- 
tion, as  one  merely  aerates  the  extra  pair  of  tubes  in 
series  with  the  same  air  current  used  for  the  ammonia 
+  urea  determination.  As  a  matter  of  fact,  one  can 
conveniently  run  as  many  as  eight  pairs  of  tubes  on 
the  same  air  current,  taking  the  precaution  at  the  end 
of  the  aeration  to  disconnect  the  series  in  the  middle 
first  in  order  to  prevent  back  suction. 

Bile. — Gmelin's  Test. — The  urine  is  superimposed 
over  nitric  acid  in  exactly  the  same  way  as  in  the 


262  URANALYSIS 

test  for  protein.  In  the  bile  test,  however,  the  nitric 
acid  should  be  slightly  yellow  instead  of  clear.  Nitric 
acid  may  be  turned  yellow  by  adding  a  few  pine 
shavings  (Emerson).  The  yellow  color  indicates  the 
presence  of  nitrous  acid,  HNO2.  In  the  presence  of 
bile  the  line  of  contact  of  the  two  liquids  will  present 
strata  of  colors  varying  from  green,  blue,  violet, 
red,  and  yellow. 

In  urine  containing  bile,  the  foam  is  always  yellow — 
otherwise  it  is  white. 

Indican. — Jaffe's  Test. — To  5  c.c.  urine  in  a  test- 
tube  add  5  c.c.  concentrated  HC1.  To  the  mixture 
add  2  c.c.  chloroform  and  5  drops  of  a  filtered  saturated 
solution  of  bleaching  powder.  Shake  thoroughly.  A 
blue  or  red  coloration  of  the  chloroform  indicates  that 
indican  was  present  in  the  urine. 

Diazo  Reaction. — Solution  A. — 5  grams  of  sodium 
nitrite  in  1  liter  water  (this  solution  should  not  be  used 
after  standing  two  weeks).  Preserve  in  glass-stoppered 
bottle. 

Solution  B. — 5  grams  of  sulphanilic  acid  and  50  c.c. 
HC1  in  1  liter  distilled  water.  Preserve  in  glass-stop- 
pered bottle.  Mix  solutions  A  1  part  to  50  parts 
solution  B. 

To  5  c.c.  urine  add  5  c.c.  mixture  of  reagents  as  above 
indicated.  Mix  thoroughly  by  shaking,  add  quickly 
1  c.c.  ammonium  hydroxide.  If  the  fluid  and  the 
foam  turn  red  the  test  is  positive.  On  standing  a 
precipitate  is  formed  leaving  a  supernatant  fluid,  which 
is  green,  blue,  or  violet.  In  normal  urine  the  reagent 
produces  a  brownish-yellow  color. 


INDEX. 


A 


ACETALDEHYDE,   157 

Acetanilid,  210 

Acetic  acid,  158 

Acetylene,  121.      See  Calcium 

carbide. 
Acids,  106 

acetic,  158,  183 

amino-,  204 

carbolic,  195 

fatty,  185 

formic,  146,  183 

hydrochloric,  83 

lactic,  169 

organic,  146 

propionic,  183 

unsaturated,  185 

uric,  245 

Albumin  in  urine,  253 
Albumins,  219 
Alcohol,  butyl,  161 

di-atomic,  162 

ethyl,  154 

grain,  154 

higher,  161 

methyl,  144 

mon-atomic,  162 

primary,  161 

propyl,  161 

secondary,  162 

tri-atomic,  162 

wood,  154 
Aldose,  170 
Alkaloids,  212 
Alum,  129 
Aluminum,  129 
Amalgam,  125 


Amino-acid,  204 
Ammonia,  202 
Ammoniated  mercury,  127 
Ammonium  acetate,  203 

hydroxide,  203 
Analysis,  volumetric,  109 
Anilin,  209 
Animal  sugar,  175 
Anode,  43,  48 
Antimony,  115 
Antitoxin,  228 
Argyrpl,  134 
Arsenic,  114 

antidote,  130 
Arsine,  114 

Asymmetric  carbon  atom,  168 
Atomic  weights,  39 
Atoms,  30 
Avogadro's  hypothesis,  40 


B 


BACTERIA,  nitrogen-fixing,  202 

Baking  powder,  103 

Bases,  106 

Benedict's  method,  254,  255 

Benzaldehyde,  198 

Benzene,  191,  192 

ring,  193 

series,  191 

Benzol.    See  Benzene. 
Bichloride  of  mercury,  126 
Bile,  261 

test  for,  262 
Bismuth,  116 
Bitter  almonds,  oil  of,  199 
Bleaching  powder,  86,  120 


264 


INDEX 


Blood,  226 

alkalinity  of,  227 

amount  of,  230 

cells,  228 

clot,  226 

functions  of,  231 

salts  of,  227 

serum,  227 

specific  gravity  of,  230 
Boiling-point,  57 
Borax,  69 
Bromine,  89 
Bromoform,  143 
Bunsen  burner,  121 
Butane,  160 


CALCIUM,  119 

carbide,  139 
Cane  sugar,  173 
Carbohydrates,  180 
Carbon,  138 

monoxide,  138 
Carbonates,  138 
Carboxyl  group,  146,  168,  169 
Casein,  235 
Catalyzers,  78,  135 
Cathode,  43,  48 
CeUulose,  177 
Centigrade,  56 
Charcoal,  138 
Chemical  change,  23 
Chloral,  157 
Chlorine,  81 

preparation  of,  81 

properties  of,  82 

uses  of,  82 
Chlormethane,  143 
Chloroform,  143 
Coal  tar,  191 
dyes,  210 
Colloids,  135,  227 
Condensation,  60 
Conservation  of  mass,  32 
Corrosive  sublimate,  126 
Creatinin,  246 
Crenation,  230 
Cresols,  198 
Crystallization,  66 
Cyanogen,  208 


DEAD  Sea,  81 
Destruction  of  matter,  31 
Developer,  134 
Dextrose,  168,  173 

in  blood,  231 
Dialysis,  135,  219,  227 
Diamond,  138 
Diazo  reaction,  262 
Diazonium,  211 
Dietary,  carbohydrates  in,  182 

proteins  in,  222 
Digestion,  carbohydrate,  180 

intestinal,  180 

mouth,  180 

pancreatic,  180 

stomach,  180 
Disaccharid,  175 
Distillation,  66 

fractional,  67 


E 

ELEMENTS,  27 
Empirical  formula,  142 
Energy,  32,  181 

kinetic,  33 

latent,  33 

Epsom  salt,  123,  124 
Ethers,  150 
Evaporation,  60 


FAHRENHEIT,  56 
Fats,  183 

body,  185 

digestion  of,  187 

milk,  236 

vegetable,  186 

Fehling's  solution,  170,  173,  253 
Fermentation,  156 
Ferments,  156,  159 

in  blood,  231 

oxydizing,  231 
Fibrin,  226,  232 
Filter,  porcelain,  70 

sand,  70 


INDEX 


265 


Flame  test,  121,  123 

Fluorine,  93 

Fluorite,  119 

Food  value  of  carbohydrate,  182 

of  fats,  187 

of  milk,  237 

of  proteins,  221 
Fool's  gold,  95,  114 
Formaldehyde,  144 
Formalin,  144 
Formic  acid,  146 
Formula,  graphic,  169 
Fowler's  solution,  115 
Fractional  distillation,  67 
Freezing,  61 


GASOLINE,  161 
Globulins,  218 
Glucose,  167,  173 
Glycerine,  162,  184 
Glycogen,  181 
Glycoproteids,  220 
Gmelin's  test,  261 
Gram,  24 
Grape  sugar,  166 
Graphite,  138 


HARDNESS  of  water,  permanent, 

69 

temporary,  69 
Heat,  60 

of  condensation,  60 

of  evaporation,  60 

of  freezing,  62 

of  melting,  62 
Heller's  test,  253 
Hemolysis,  230 
Hexane,  171 
Hexose,  170 
Homogenized  milk,  236 
Honey,  170 
Hydrated  lime,  21 
Hydrocarbons,  saturated,    160, 

163 
Hydrogen,  48 


Hydrogen,  nascent,  49 

peroxide,  77 

properties  of,  49 

uses  of,  49 
Hydrolysis,  174 
Hydrometer,  55 
Hydroxyl,  73 
Hygroscopic,  121,  162 
"Hypo,"  134 
Hypobromite  solution,  257 


INCOMPATIBLES,  75 

Indican,  245 
test  for,  262 

Indicators,  108 

Indigo,  209,  210 

Inversion,  174 

Invert  sugar,  174 

Invertase,  174 

Iodine,  90 

preparation  of,  91 
properties  of,  92 

lodoform,  143 

lonization,  73 

Iron,  129 

Isotonic,  229 


JAFFE'S  test,  262 


KETOSE,  170 
Kjeldahl,  225 


LACTASE,  175 

Lactose,  175,  236 

Laking  of  blood,  230 

Law  of  combining  weights,  36 
of  conservation  of  mass,  32 
of  constant  proportions,  35 
of  multiple  proportions,  35 

Lead,  133 


266 


INDEX 


Levulose,  170,  173 

Light,  polarized,  167 

Lime,  19 

Lipase,  187 

Liquor  chlori  compositus,  82 

Lithium,  110 

Litmus,  85,  108 

Lunar  caustic,  133 

Lysis,  174 

M 

MAGNESIA,  124 
Magnesium,  123 
Malt  sugar,  156,  175 
Manganese,  131 
Mannite,  166 
Marsh  gas,  141 
series,  153 

test,  115 

Marshall's  method,  257 
Melting,  62 
Mercury,  125 
Meta  compounds,  195 
Metals,  25 
Methane,  142 
Methyl  acohol,  144 
Milk,  235 

clot,  235 

cow's,  237 

human,  237 

salts,  236 

sugar,  175,  236 
Mine,  damp,  141 
Moisson,  138 
Molecular  solutions,  106 
Molecules,  30 
Monosaccharid,  170 


N 

NITRIC  acid  test  for  albumin' 

253 

Nitro  benzene,  193 
Nitrogen,  202 


OIL  of  bitter  almonds,  199 
corn,  186 


Oil,  cottonseed,  186 

olive,  186 

peanut,  186 
Olein,  185 

Ortho  compounds,  195 
Osmosis,  228 
Oxidation,  27 
Oxides,  45 
Oxygen,  26,  43 

preparation  of,  43 

properties  of,  44 

uses  of,  44 
Ozone,  46 


PALMITIN,  185 
Para  compounds,  195 
Paraffins,  160 
Paraldehyde,  157 
Pentane,  160 
Pentoses,  172 
Petroleum,  160 
Phenol,  195 
Phenylhydrazin,  210 
Phosphorus,  112 

effects  of,  113 

forms  of,  113 

uses  of,  113 
Phot9graphy,  134 
Physical  change,  22 
Plasma,  226 
Plaster  of  Paris,  120 
Platinum,  134 
Polariscope,  167 
Polysaccharid,  173 
Potassium,  109 

permanganate,  131 

sulphocyanate,  209 
Pressure,  osmotic,  229 
Pyridin,  213 
Priestly,  27 
Propane,  158,  160 
Proportions,  constant,  35 

multiple,  35 
Proteids,  218 

compound,  219 
'   derived,  220 

glycoproteids,  220 

simnle,  218 
Proteins,  216 


INDEX 


267 


Proteins,  classification  of,  218 

digestion  of,  220 

occurrence  of,  217 
Pro-thrombin,  232 
Purification  of  substances,  66 
Putrefaction,  156 


QUICK-LIME,  19 


R 

RADICAL,  organic,  144 
Reducing  power,  169 
Reversible  reaction,  51,  119 
Rusting  process,  25 


SACCHAROSE,  173 
Saline,  101,  230 
Salt,  102 
Saltpetre,  110 
Salvarsan,  115 
Silver,  133 
Soda,  103 

lye,  104 
Sodium,  100 

chloride,  102 

hydroxide,  104 

Solubility,    effect   of    tempera- 
ture on,  65 
Solutions,  64 

Fehling's,  170,  173 

hypertonic,  229 

hypotonic,  229 
Specific  gravity,  55 

of  urine,  240,  250 
Spectroscope,  124 
Spectrum,  124 
Springs,  68 
Starch,  176 
Stearin,  185 
Strontium,  121 
Structural  formula,  142 
Sugars,  165 

of  lead,  133 


Sugars,  reducing  of,  in  urine, 

253 

Benedict's  method,  254 
Fehling's  method,  253 
Sulphocyanates,  209 
Sulphur,  95 

dioxide,  97 
Symbols,  28 


TARTAR  emetic,  116 
Thermometer,  56 
Thrombin,  232 
Toluene,  197 
Toluol.    See  Toluene. 
Tonicity,  229 


URANALYSIS,  249 
Urea,  243 

constitution  of,  244 

estimation  of,  257 

hypobromite  method,  257 
urease  method,  257 
Van  Slyke's  method,  257 
Urease  method,  257 
Ureometer,  257 
Uric  acid,  245 
Urine,  240 

acidity  of,  252 

albumin  in,  253 

amount  of,  240,  250 

collection  of,  249 

color  of,  241,  251 

odor  of,  241,  252 

organic  bodies  in,  243 

preservation  of,  249 

reaction  of,  242,  252 

salts  in,  242 

specific  gravity  of,  240,  250 

total  solids  in,  251 
Urochrome,  241 
Uronoid,  241 


VALENCE,  97 

Van  Slyke  method,  257 


268 


INDEX 


Vinegar,  158 

method  of,  158 
Vitamines,  213 
Volumetric  analysis,  109 


W 

WATER,  53 

composition  of,  72 
hard,  69 
potable,  70 
properties  of,  54 
rain,  70 
river,  68 
sea,  68 
soft,  69 


Water,  as  standard  of  compari- 
son, 55 

synthesis  of,  72 

uses  of,  54 
Weights,  24 
Wood,  177 


XANTHOPROTEIC  reaction,  218 
X-rays,  117 
Xylene,  197 
Xylol.    See  Xylene. 


YEAST,  155,  174 


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